Hello! I've got a 1989 Ford L9000 dump truck with a Cat 3306B engine in it. While I was running up through the gears the other day, the engine just stopped pulling. It didn't quit outright, but wouldn't accelerate no matter the throttle position. I pulled over and parked, and the engine then slowly dropped below idle and died. I shut off the key switch, turned it back to run, and it fired right back up. No hesitation, ran great! It has done this a couple of times since, but always fires right up after stalling. I have changed both fuel filters, cleaned the fuel tank, and replaced the fuel pickup hose to the tank. I have a transfer pump on order, I have not checked delivery fuel pressure yet. The issue seems to happen at or above 3/4 throttle. Just strange how it will instantly fire back up. Any ideas? Thanks for any help!
Electrical shutoff switch failing? Check the wiring harness connections.
When this happens is it producing black smoke or zero smoke?
The shutoff solenoid seems good, I hear a solid click from it when I turn the key on and off. I cleaned the terminals on the solenoid itself and made sure it has good power and ground. Is it possible for one to partially fail? Once parked in neutral, engine speed slowly drops until it stalls, unlike shutting the key off. I see no smoke once it starts losing power.
How many hrs/miles on engine?
Not sure on hours, but it has around 165,000 miles on it. Runs strong other than this issue.
Is that shutoff solenoid powered through a relay that could be bad?
Yeah it probably is controlled with a relay, I'll trace the wiring once I have it back in the shop. It's kind of annoying, I have a Ford L-series shop manual, but it doesn't make any mention of the Cat 3306 engine.
Is the tether chain still on your fuel cap? If not, I'd remove the suction line and standpipe. I'll bet there's trash in there.
So I did drain the tank and clean it thoroughly, kind of convenient that the filler neck is arm-sized lol. I also replaced the fuel suction line, but wasn't able to remove the pickup tube with the tank mounted on the truck. Cap tether is still present. Kind of wish I would've pulled the tank when it was empty and checked that pickup tube now.
I just don't see it restarting and back to normal so quickly if it was a fuel restriction.
That's what has seemed odd to me too, it fires right back up and runs fine until the next time you get past that certain point in the throttle. Engine load also plays a role. I'm interested to see what it does once I replace the transfer pump, it's a plunger style one driven off the injection pump camshaft. I'll also be able to inspect the steel fuel lines at the same time.
So as the fuel draw increases, it pulls whatever is in the pipe up to the elbow where it piles up and restricts flow. Once shut down occurs, junk relaxes and fuel takes its place.
Is it the kind you just pump furiously to prime and let it be, or is it the one you gotta lock down when it primes up. Those o-rings do get dry and leak air. The other thing to be watchful of is hidden racor fuel water separators or fuel pro . Those things will also suck air, but usually leave a fuel/dirt residue behind.
I see what you're saying about the pickup tube, I will definitely investigate that. It does have a priming pump, it screws down and locks. Would it be able to suck air screwed down? It does have a water separator, it's factory though. I replaced the o-ring that seals the bowl on it this spring. Thank you for your help, I appreciate it.
Worst case scenario, if you don't find any obstructions, you can pinch or plug your return line. Apply 3-5 psi of air pressure to your tank with the vent plugged. This will force fuel throughout the system. Any external leaks that show up are sources of air intrusion. You must be careful when pressurising your tank. It's not designed for positive pressure. It will oil-can or knock rust off and leak, so be extremely cautious.
Great idea about pressurizing the tank, I will give that a try (carefully).
Can anybody tell me whether the injection pump on this 3306 is a sleeve or scroll metering type? Engine serial number is 63Z14319. Thank you!
If it's like this one, it's a scroll type pump. I think they call it new or improved scroll type pump. The old scroll type pumps from the 60s and 70s were much narrower. Another look at it from one on Ebay:
Okay, update time. So I got the truck in the shop this morning. First thing I did was pressurize the tank, regulated at 6 PSI. Everything held pressure, soap tested all connections and the bowl on the primary filter, no leaks I can see. I just got done testing delivery fuel pressure to the pump, has a solid 30 PSI at idle, which I believe is within spec. I'm going to pull the supply line off of the primary filter housing and place it in a bucket, then apply pressure to the tank and see what I have for flow from the tank. I was kind of hoping I'd see low delivery pressure. I have a new lift pump coming tomorrow, I think I'll go ahead and install that anyways. Any more ideas? Thank you everyone for the help so far!
You need to measure fuel pressure full throttle under load. For example, raise the dump bed at relief to place some load on it. Idle doesn't really tell you anything.
Alright, two more thoughts...the secondary filter is new, but it is a Fleetguard FF5320 2 Micron filter. Is it possible the filter is too restrictive? I wonder what filter CAT specifies and if it's possibly less restrictive. Also, the secondary filter base is bolted to the side of the injection pump. Is there possibly a screen between the filter base and pump housing?
Okay, I will try and get a loaded pressure reading. I wish I could raise my bed inside the shop, darn low ceilings.
I think we should hope that thepumpguysc sees this and adds his knowledge. I don't think anyone is more knowledgeable with the mechanical fuel systems. That said, a 2 mic filter should pass enough fuel till she begins waxing. I don't think we've been that cold yet?
Yeah I've read some of his posts, I bet he could be quite helpful. Could I message him and ask him kindly to take a look at this thread? Also, more updates. Flow from the tank looks strong. I had maybe 5 PSI on the tank, and had a strong solid stream of fuel coming out of the pickup hose. Just for fun I vacuum tested the air/fuel ratio control on the back of the governor, and it will not hold vacuum. There was also a bit of oil in the fitting. I believe this points to a bad diaphragm in the afcr. I don't know if this is my issue, or a separate one. Interesting...
Well, AFC operates under positive pressure not vacuum. I can't say that test or it's results have any validity. I don't see why you couldn't PM him. In fact he has cryptically given out his email address many times on various threads. Don't be mislead by flow under pressure, it's different than flow under draw. You wouldn't think so, but it is. You've got all I have to offer, now I defer to the specialist.
Haha fair enough, well thank you for all of your help so far funwithfuel, I really appreciate it! I will try and get in contact with thepumpguysc and see where he leads me. It's been a great learning opportunity thus far, if nothing else.
Easiest way to get someone's attention on a thread is like this: @thepumpguysc @Cory W Now it sends an alert to him that he was mentioned, and he'll probably come and see what was said.
BTW, how did the standpipe check out?
Thanks! I wondered how to do that lol
So I wasn't able to remove it for inspection, but I was able to put air through it no problem. I also assumed it was clear after I pressurized the tank and had a solid stream of fuel out of the fuel line.
Did you blow through it backwards and see if trash popped out?
I've mentioned this one before. A fleet of grain trucks we took care of all powered by E model and up Cats-one had a issue exactly like this 3306. Ran great till 3/4 throttle, would idle all day, as long as no 105,500 gvw was put to it-it was fine. Checked fuel lines, check valves in primer and filter base, checked fuel pressure from lift pump, checked electrical system, you name it-was all fine. Let it set idling with gauge hooked to filter base, throttled it up about 7 different times. On the seventh the fuel gauge dropped engine died. Went to fuel tank, looked inside with light, a long something was laying in bottom. Drained tank, using grabber finally got ahold of it. It was the thin 1 1/4 wide micro board from the center if a old tube type fuel sending unit, just enough suction would pull it to the pickup tube at high throttle. Freak. I doubt yours has that type of sending unit. But don't go down a rabbit hole installing parts till every part to fuel system has been checked. Sandwich bags in tank really play hell.
I have to admit, I'm really curious of that pickup tube now too. I couldn't see anything when I put the air to it earlier because the tank is still about half full of fuel. I will try and get it pulled tomorrow for inspection. Unfortunately the tank has to be removed in order to access it, but it'll definitely be worth knowing whether or not the pickup is the issue. Honestly I hope it is, that'd be a nice way to wrap up this problem!
Alright, the results are in! I pulled the fuel tank this morning. Turns out the pickup tube is integral on this tank, so I couldn't remove it. But I was able to shine a light in the tank and look down through the tube and....free and clear, no obstructions. I'm glad I can rule that possibility out though. Going forward, I plan on replacing the lift pump which I received today, and I will clean the fuel hard lines while they're off. Anyone want to take another poke at the pig?
So, standpipe is clean as a whistle. Running fuel pressure ~30psi @ idle. AFC diaphragm leaks oil in vacuum test. Fuel filters are clean and new. Pressurizing the fuel system with the return line dead-headed shows no leaks. Running @ 75% or more throttle, she bogs down to the point of dying but continues running. Have you checked fuel pressure at full throttle, loaded?
It's almost like something that turns the fuel on and off is not working correctly.
I like this condensed version, yeah that pretty much covers it. The only thing is once it starts to lose power, it will always die. It never picks back up until it quits and is restarted. I plan on road testing the truck today with my pressure gauge hooked up and see what fuel pressure does. I can duplicate the problem pretty well, bottom of seventh gear with heavy throttle almost always does it.
Most definitely, are you thinking fuel shutoff solenoid or air/fuel ratio control?
A problem with the AFR will not allow it to build boost pressure. I've never had one affect the idle or make the engine die. If it's not revving then eventually dying, but will start right back up and run perfectly without cranking and cranking after cycling the key switch then I'd be watching the voltage to the shut off solenoid while you're on that road test.
So when it's bogging down, is it still running because the running gear is turning via the clutch engagement. If you were to push in the clutch , would the engine recover or fall flat?
I would lean towards it either being a fuel shutoff problem or an internal governor problem. The governor flyweights on these can wear into the thrust washer and cause the rack to stick. Usually causes more erratic rpm problems though. Most of the 3306 engines can be run with the shutoff removed and capped then just shutoff with the throttle linkage. You could try that to eliminate a shutoff problem. The blocked fuel line idea could cause it too but I think you have covered that. Can you run it down the road with a fuel pressure gauge run into the cab?
My thought is if it's a fuel shut off solenoid-it wouldn't slowly die. Normally when the solenoid take a dump-it's engine off right now. I've had those were I just cut the rod off and screw it back in to get it to the shop.
First off, I want to say thanks to everyone again. Really helps being able to bounce ideas around. Yes the only reason the truck stays running is because it's coasting with the clutch engaged. If I push the clutch in, the engine will slowly die out. I think a bad fuel shutoff would cause a more instant shutdown too, but I'm planning on removing the solenoid and driving it. I will also run my fuel pressure gauge up where I can see it while driving. I'm currently working on swapping the fuel tanks around due to a pinhole leak I discovered during my pressure test (oops). With any luck I should be able to drive it today yet. I will report back with any news
Yes, either the switch is good or it's bad. But if he has intermittent low voltage from bad relay, uninsulated wiring touching somewhere, poor connection at source (he said he checked termination studs), sudden high resistance...or intermittent loss of ground? Is the engine or transmission moving around when it gets in a good pull and rubbing on the shutoff wiring? Is the engine ground strap connected to the frame and/or cab? I think it would be best to remove the shutoff and road test.
I have a new fuel shut off solenoid on the shelf, using a old heater motor rheostat switch and digital meter it operated every time the voltage raised to 9.9 to 10.1 volts. That's this one, I can't say it would be the same for all.
That's the way to do it.
So I didn't get to drive the truck today, swapping the tanks around and cleaning everything ate up more time than I would've liked. But everything is set for tomorrow; fuel pressure gauge plumbed in and truck starts and runs. I'm going to go for a baseline ride to verify the issue is still there (wishful thinking) and check fuel pressure. Then I'll remove the shutoff solenoid and see what it does. I know I'll lose oil with it open, any suggestions on how to close it up? Also, Mobiltech mentioned shutting it off with throttle linkage, pushing the linkage in the idle direction will kill it?
Just make a temporary blockoff plate out of some scrap steel. Use a long temporary stud in the back of the pump for ease of reinstallation of the plate and later the switch. Sometimes those switches are hard to get at. Just put it in high gear and let out on the clutch to kill the engine without the shutoff switch.
So I finally went for a ride this morning, problem is still present. Engine runs great under light to moderate load. Once I get up to seventh gear (8LL transmission) if I go beyond 3/4 throttle and put a load on the engine, it loses power. I can lightly throttle all the way up to the governor in 7th or 8th and be fine, so it's definitely load related. Just to be clear, the truck is empty, just moving itself. Tried removing the shutoff solenoid, no change. Fuel pressure at the secondary filter sits right around 30-35 PSI, no change in pressure once it loses power. I'm going to remove and inspect the steel lines to and from the lift pump, and change the lift pump while I'm there. I might even pull the filter bases off and inspect them as well. Looks like persistence is key on this one.
I also plan on replacing the diaphragm in the air/fuel ratio control once I get gaskets. I know it's most likely not related, but should really be fixed as well.
Sounds a little strange but I think it’s heading towards a sticking rack or governor issue. One other thing that crossed my mind is a possible intake air hose collapsing and acting like a positive air shutoff. Is there an air to air aftercooler on this? Is there a hose before the turbo that could collapse? I had a 3304 in a hoe years ago that under load would collapse the intake hose and kill the engine. It would start right back up and run okay until you loaded it heavy.
It does have an air to air after cooler. Good suggestion about the intake hose, I had to go and look! It's a plastic molded tube from the air cleaner to the turbo inlet, doesn't look like anything that could collapse under vacuum. I'm not very savvy on how the governor or fuel rack operates so forgive me if you would. The rack is always trying to add more fuel, and the governor pushes back against it to limit fuel depending on rpm/load?
I changed the fuel lift pump out this afternoon and cleaned/checked the steel hard lines going to and from the pump. Drove the truck, problem is still there. Looks like the new pump gave me a small bump up in pressure, sits around 38-40 PSI now. I've got parts on order to fix the AFRC, not holding my breath though. If that doesn't do anything, I might look into the governor/injection pump. I might also just drive the thing, I've used it all summer and it still runs great besides this problem. Oh well, happy Friday!
The rack won’t do anything on its own. It stays wherever the governor weights put it. When you step on the throttle you are compressing a spring that is fighting against the flyweights to give the pump a higher rack position. The higher the engine rpm goes the more centrifugal force the weights generate until they overcome the governor spring pressure and push the rack back towards less fuel. There is a thrust washer and bearing between the weights and spring that can get worn and cause the weights to stick. When the thrust wears the engine starts to run like a wound up rubber band as the load comes on it just drops rpm until it stalls because the weights can’t react to keep a steady rpm. If left too long it will run away at some point. The governor can be disassembled on the truck to inspect the weights and washers but it is easier on the bench. The trick is to find someone who has had one apart then it’s not really a big deal.
Isn't there a Cat tool group for this pump?
Nothing special is required for the governor end of the pump. It runs in engine oil. A 7/16 socket gets most of it apart. Its knowing what to look for when you're in there that takes some experience. The special tool is for plunger and barrel removal which you would want the pump removed for.
I'm thinking 3406 I guess.
Thank you for that explanation Mobiltech, that helps me picture it a little better in my head. I don't like tearing into things without understanding how they operate first. I ordered a service manual for the 3306B yesterday, so that should be helpful as well. We'll get to the bottom of it eventually!
I’m thinking it’s a governor issue, as well. The slight wear required in the flyweight assembly to cause that problem is so subtle, it’s difficult to detect unless a experienced Cat guy points it out.
As it turns out I may have found a guy locally who knows cat engines, maybe I'll have him take a look at the governor. Is the governor difficult to remove from the injection pump? As in, can I pull it off of the pump in the truck and not have a bunch of parts fall out? Looks like a few long 1/4" bolts holding it onto the back of the pump. What type of seal is there between the gov. and pump? I got parts to fix my air/fuel control, I'll do that next week just to fix that problem. The governor is about the only thing left to check at this point.
As it turns out I may have found a guy locally who knows cat engines, maybe I'll have him take a look at the governor. Is the governor difficult to remove from the injection pump? As in, can I pull it off of the pump in the truck and not have a bunch of parts fall out? Looks like a few long 1/4" bolts holding it onto the back of the pump. What type of seal is there between the gov. and pump? I got parts to fix my air/fuel control, I'll do that next week just to fix that problem. The governor is about the only thing left to check at this point.
The governor is an integral part of the FIP. Can't be removed as a unit but if access is OK, it's not too difficult to dismantle in-situ.
I’ve never been brave enough to fiddle with one on the engine. I always remove the entire fuel inj assembly and work on the bench or the bilge plates. But guys do it and much respect to those salty fellas back in the days of yore when average men of above average character kept these iron dinosaurs running.
You will need a Pony 3202 clamp modified like this to remove the watchamacalit spring. The manual explains it. I quoted 16 hours to R&R and rebuild pump & governor back when I was doing them on a regular basis. Not a bad job. I enjoyed doing them. I keep my Cat fuel system specialty tools in the silverware drawer, next to the pepper sauce. How about you?
The governor flyweight spring cover is not reusable. Even if you think it is. If you bugger the new one even slightly, the flyweights will jam and the engine will rev to never-never land. But, your mileage may vary.
This video shows the separation of the governor on a dozer of the same type as yours, and what you're going to see on the inside. I'd also take a look at the supply and return fuel lines to make sure that someone hasn't accidentally swapped a line around. Not sure what your history with the truck has been.
Wow that’s a terrible video. I didn’t watch it all but I gather he took it apart to adjust fuel settings which you do not do. Fuel settings are easily done through the fuel setting cover on the back. I would say don’t touch the governor yourself as it can go horribly wrong if you don’t know what youre doing. Let your Cat guy do it. If anyone is in the governor make sure you have an intake pipe off and a board to use as a blocker plate for startup in case it runs away.
Yeah I think the internal governor work would be best left to someone who knows what they're looking at. My biggest fear is having to put a new $5,000 injection pump on my 33 year old $9,000 truck. The only parts of the fuel system I haven't directly removed and inspected are the primary and secondary filter bases, and the priming pump. When I prime the system I can feel the primer pump fuel, and I can hear it running back to the tank through the return line. The priming pump does not build pressure though. From what I understand this is normal, the return is a metered orifice back to tank. Something like 7 gal/hr. Am I correct on this?
Thinking more about the symptoms you described and looking back on 3300’s that kicked my butt in the days of yore. I think you might be dealing with a broken guv’nor spring or worn or notched flyweights/pins. Yeah, there are so many things that can go wrong during the process of fixing one. Having a way to shut down a runaway is critical. Like Dirty Harry said- “A man’s gots to know his limitations”.
6V2163.
That’s the one! Always replace the carrier screws with new. I just remembered that. A small seal driver for the governor shaft seal on the rear housing. Very few special tools needed.
For 3406-the tool group I was thinking of 6V6070.
Alright so kind of an interesting update...I got the parts I ordered for the air/fuel control installed this morning- specifically a new diaphragm, adjustment cover gasket, and plunger seal...I don't really know what to call that. It's a cup type seal on the actuator rod that sticks out of the end of the control unit. Pressure tested it to 20 psi, had a very slight leak until I depressed the actuator rod, then it stopped...don't know what to think of that. Installed control, and drove the truck. Seemed to be a bit more responsive, but still drops power in the same throttle range. But now instead of stalling once the revs drop, it will idle. Still doesn't run right after it drops out, lacks power off the line...but it doesn't die like before. As before, I can shut it off, fire it up, and it runs fine again. Still scratching my head on this one, what do you guys think?
Talked to a good friend of mine 32 year ex Cat man. He primarily worked 3406/3306 years back. Ran through all your symptoms. He agrees it's pump related but It defiantly needs expert cat attention. He said being a 89 with X amount of hrs/miles it truly should be removed and completely redone/inspected. As far as flyweight pins those can be a issue but the reality is those can and do break which puts a hole through the side. He brought up the fuel return defuse'r plate on main housing under the long main housing side cover those can deteriorate and cause issues. He's a very picky Cat mechanic, worked Spokane, Pendleton and Pasco Cat Shops.
Thank you for taking the time to talk with your friend, I appreciate it. Yeah I'm about at the end of what I can do myself, I don't want to attempt any governor work myself. I will have a service manual soon, I may look into removing the pump assembly and taking to someone who knows what they're doing. I'm done hauling for the year, so it'll be on bedrest until spring. Big job in the spring, should be all set by then!