Hi all new to the forum here and looking for info on an A25C. The problem I'm having is that when you put the truck in gear it won't really rev up and go anywhere. If you just move it around at idle it will move fine, but if you try to accelerate it just bogs the motor down and has no power. The Motor was rebuilt when we got the truck and seems to run good, other than revieg up a bit slow from idle. This kind of leads me to believe it's something with the trans, like possibly the retarder being stuck on (if that's possible) I don't know if anyone here has any experience with this situation, but even some direction as to a possible cause would be helpful.
Got fuel, how bout boost?
What does in do in Neutral.. rev normal or bog.?? THAT'LL tell u if u have a fuel or trans problem.. IF it revs normal, chances are its trans.. IF it bogs & is slow to accelerate its fuel..
Seems to be getting great fuel pressure haven't checked for boost yet. Is it possible for the exhaust retarder to get stuck closed on these?
In neutral it revs up but from idle it's slow if you rev it in stages it acts normal. I didn't know if that was normal for these motors or if there was a problem, because other than slow reving from idle it seems to run really good, and it starts really easy.
Check the over-flow valve on the inj. pump.. they come loose internally all the time. Take off the return line banjo bolt & w/ a screwdriver, reach in to the center of the ofl vlv & see if the screw is loose or tight.. IF its tight, leave it alone..
What engine is it?
Does it sound like the retarder is stuck on? It's a very distinct sound. Has it been like this since rebuilt? Are any of your pumps getting hot?
It doesn't have the distinct whine of an exhaust brake, but I didnt know how these systems would sound. I believe it has been this way since the rebuild, but I'm unsure how it acted before. When you say pumps do you mean the hydraulic pumps on the trans?
The engine is a Volvo TD73KCE
Yes, if the pumps are loading by a false load sense signal it'll bog the engine. The engine should be able to power through with sufficient fuel n boost. Now if you're hearing a loud rushing noise as opposed to a loud hissing noise, you may be looking for a ruptured boost hose joint to or from the cooler. What kind of smoke you seeing?
By your description, I'm leaning toward retarded injection timing
I am not really getting any smoke it will just puff out a little light grey smoke occasionally.
I checked the valve and it was tight any other suggestions?
Fuel water separator bowl tight?
With retarded timing would it still start good?
Yeah its tight and looked clean. Do these engines have an aneroid adjustment, now that I've been thinking about it isn't it a little wierd I'm not getting any smoke at all?
Yes, low fuel pressure = white smoke, low boost = black smoke. Little whisp of grey usually indicates ok. Does the engine sound like its laboring to climb up in rpm? If not, I'd see what I could do about confirming pump timing.
It does seem to labor a bit when climbing past 1500 rpm, but not a ton. What's the best way to confirm timing on these motors?
IIRC timing window on flywheel housing . Take an 8mm grind a point onto it and screw into 3rd hole. Open pointer cover on pump. I do not know what spec is. It may be on engine ID tag. When pointer is centered in window, timing should point at desired degrees
The timing off-set is built into the pump.. SO.. when the PUMP POINTER is centered in the window.. the ENGINE will be at TDC.. The aneroid does have a star wheel but the access is under the TOP cover or thru a SIDE cover.. Those engines are always under powered & I always turned them up 10% AFTER I got done TURNING THEM UP to spec.. They were like "race cars" when they gottm back.. Lol
When you say pumps pointer where is that on the front of the intermediate shaft going to the pump or through the hex plug on the side of the pump, or am I just missing it completely?
Its that 8mm plug below & to the right of the return line.. below the shut-off lever. Its gonna be TIGHT.. rap it a couple times w/ a hammer & brass drift 1st. How are the rpm's?? almost every one I've worked on is way low, on max no-load rpm's.. {& fuel}
The rpms seem to reach full throttle (around 2500).
Is there supposed to be oil in this section of the pump?
Yes, oil in that cavity.
How do you see in the pointer do you have to remove the coolant pipe?
well you're really supposed to have an AB light. its a tool you screw in in place of the plug and has two sensor probes that wait to "feel" the pointer coming by. When both A&B light up you are dead nuts on. In the interest of down n dirty you could just watch for it with a mirror and light.
What will the pointer look like when it comes by?
A pointy arm pointing right at the window
Is there a specific spot to bar the engine over with or are you just supposed to use the front of the crank?
On the exhaust side of the answer in the bell housing front face there should be a 10 plug with I believe a 22 or 24 mm recessed hex . One of those is in line with the edge of the fly wheel with an engine turning tool or pinion you can turn the engine over easily from their otherwise you are stuck trying to turn it from the front of the crank damper. Some of the older machines even had a whole then aligned with the crank bolt so that you could put a long extension in there and turn it from outside the frame
Yup, special turning tool from access plug in flywheel hsg. OR.. crank IF U WANNA KNOW when your GETTING CLOSE, remove the hex head plug up towards the drive on the side of injection pump{12mm?}.. When it STARTS TO RISE, your on #1 compression stroke & start looking in the timing hole for the pointer..
You guys are gooooood!!!!
Is this the pointer in the pump
Yes that is the little fella you're looking for now what is the pointer showing on your flywheel timing degrees
You can jump in any time you know
Timing is set at 8 degree s which is what's specified on the valve cover.
Oh hell, I'm enjoying the ride-along!!
OK now you've learned something valuable and you verified that your timing is correct . next up is put everything back together let's fire it up and see will kind of boost your building. Find A pipe plug or nipple or something between the intake manifold and the turbocharger were you can gauge boost pressure while you throttle up. It would really be nice if you could put a 100 pound gauge on your fuel supply system after the lift pump also to verify that you have adequate fuel pressure to your injection pump.
8* before or after? Gotta be sure.
One other thing that has me concerned I looked at your picture again is the screw in your stop cable hitting the case of the pump or is it free to go travel further forward. It almost looks like it's hitting the main body
G. DAM GOOD CATCH FWF.!! THAT s/o lever should be hitting the overflow valve..!!!! Its partially ON..
Well let's see if it bares fruit
What do you mean before or after, before or after the 8th degree mark on the flywheel?
So the shut off lever should be able to go forward far enough to hit the spacer on the return line?
TDC before or after top dead center.
Maybe not actually hit it but further forward than in picture
The "spacer" IS the overflow valve.. {I thought u checked it.??}
I did I just thought it was built into the pump and there was a spacer after it, but yeah it was tight.
Before
Make sure that the shut off is properly applied when the engine is running
Just unhook the cable & SEE if it goes forward & hits the ovflo vlv.. They mighta lost the woodruff key & clamped the lever down to the shaft.?? I'v seen THAT about a bazillion x.. That key is T I N Y...
The shut off lever goes all the way forward and stops itself before the cable does.
Does anyone know what the pressure coming out of the aneroid air line should be?
Its usually 14-17psi minimum at full load rpm.. DID U UNHOOK the shut off cable.??
The A25C takes a 13/16 ** socket to turn the engine via the front of the crank its not Metric as a point of interest, the Load Monitor control would be worth checking to see if its indexed correctly, the fact the engine revs up freely out of gear ( I take it) would indicate that fuel etc would be O.K. the exhaust brake and turbo would then be of interest to check, the turbo simple check is on the small connecting hose to the after cooler, rev the motor up and the hose will expand and be solid, the gearbox is fitted with a retarder (left treadle) that can play up some, even with packed dirt under the treadle, the same can happen to the throttle control making the low idle speed to high resulting in no gear select, the shut off cable is connected to the hydraulic oil feed control lever.
Do you check the hydraulic pressure, be sure that the stand-by pressure is ok. Stand-by connected (35-55 bar) 507-598psi stand-by diconnected (24 bar) 348psi Max pressure (210bar) 3045psi
Yep and the s/o lever goes all the way forward. When you say full load rpm does that mean no load (neutral/ not driving) full throttle, or is that when your really working it hard?
Ok so some news on the fuel and boost situation. Boost: I drilled and tapped the crossover pipe (off the truck) to pipe thread so i could use a small gauge. When I checked boost at full throttle I got about 6 lbs. Unfortunately I don't know how accurate this small gauge is other than it compared pretty close to another gauge when I tested it with an air hose. Fuel: for fuel I get a round 30 lbs at idle but it jumps around, and at full throttle I get about 50 lbs. Checked from bleed screw on top of filter housing. One thing I did notice about the fuel system though is I'm getting some air bubbles in the fuel strainer cup on the side of the pump, is this a normal occurrence?
That is a common problem. I asked early on about the fuel water separator. If it's the one with the glass bowl, they're prone to air intrusion. The rubber gets dry rot and cracks. The little plastic drain cock gets wonky too. And the seal for the screw that runs the center. The pressure sounds good. As long as its liquid fuel and not foamed. Can you run an alternate fuel source to the lift pump?
Well this model has the plastic fuel water separator, and I checked it again today, but I couldn't find any cracks, it has a new O ring on it, and I couldn't find any leaks when I blew air into it. Is it normal for the primers on these pumps to have fuel leak out of them when you use them? Because it does that sometimes. Is that really all the pressure you should get in the intake manifold? Yes I should be able to hook up an aux line to the lift pump.
Can you post a pic of separator? Let's continue with other source of fuel in meantime. Leaking fuel @ primer pump might need a new primer pump. They are prone to failure. The plunger does screw down tight though, right?
Pressure on intake sounds ok. Boost builds under load. So if you were in gear, you'd have been up near 25-30.if your fuel is up to task.
Do you lost the fuel pressure when the engine is loaded when the problem of RPM on the engine has started ? When the engine is hot the low idle spped showl be to (665 - 715) rpm
Well I can't really load the engine down, but when I just revved it up no load it got around 50 psi fuel pressure. The idle speed seems about right I don't have the most accurate tachometer but the readings I got were real close to what you indicated.
What is it when u drop it in gear & try to move.?? THATS the important part..{pressure}
The radiator fan should be at 700-900rpm when engine is at idle speed , when the engine exceeds 1500rpm , the fan motor speed will increase to 1400+ or - 50rpm
how did the engine problem happen ?, the machine working fine and the problem happen ? did you do some repair on the machine before the problem happen ?
I looked, the primer isn't one that can be screwed down ( I think I couldn't feel it engaging on any threads) This is the seperator
The base of that sediment bowl looks like it has fuel/dirt accumulated. Find that source. Next the primer pump, if it leaks, change it. Because when it's not leaking fuel, its sucking air.
So I did another few pressure tests and discovered that the fuel pressure is not consistant at all. So I've got the lift pump off trying to find a replacement and see if that helps. As for the primer I was able to find one that was similar and screws down unlike the original. Hopefully the new lift pump will also come with a new water seperator so that can be ruled out. Any other things to check right now for my problems, or just wait for the pump and see?
The supply pumps can be rebuilt.. just take it/send it ,to your local fuel inj. shop.. & they'll put a new HP on it too.. The part # is etched into the hsg next to the HP.. so don't go thru a "middle man" to get/buy 1..
Quick update: found a new pump oe for a decent price should be here in about a week. I'll have to wait and see how it works out and tell you guys what happens. I will probably have more questions about this truck but for now ill just hold off to see what the pump does for it. Thanks for everything so far everyone!!
Hi again everyone Some news on the truck: I got the new pump and installed it today. The truck does seem to run better than before, but im still getting air in the fuel seperator bowl. The lines from the tank look good and the fittings are tight so I think it may be a suction problem in the tank. I will check the lines over more carefully, but does anyone know how the fuel suction is set up in the front tank, and how to remove the fitting, does it just screw out?
Yep, long stand pipe brazed in fitting iirc. Just make sure you have 2-3 feet clear directly above for removal. Could be a corroded pipe.? Try alternative fuel source to see if it improves
I'm a bit late to this party but here goes. I guess this truck has the butterfly style exhaust brake? If yes, read on. Many years ago I got a call out to an old Volvo ADT (can't remember the exact model) with the same problem you're having. The story was that the turbo failed, someone replaced it and then the truck had no power. Long story short, I eventually found that the exhaust brake had been installed wrong and the valve was shut when in was supposed to be open. I suggest you give it a look.
Hi all, I know it's been a long time since I posted, but I finally have some spare time to work on the truck again. Previously I'd been so busy that I had to put this project on the back burner. Since the last time I posted I checked the fuel feed line from the tank (with a vacuum brake bleeder ) and it held good vacuum. I also checked the suction pipe inside the tank, it was good, but the return line was at the same level as the pick up. I shortened it up thinking that the pickup was just sucking airated return fuel, but then I started it a while later and I'm still getting air bubbles in the water seperator bowl, and my fuel pressure is all over the place. So any ideas on what the problem could be? I'm going to hook up a separate can to run fuel from later today and see if that changes, but is there any other possible reason for this, especially with a brand new lift pump?
The "lift pump" supply fuel BUT the "Overflow valve" HOLDS the pressure to a preset limit & then lets it go.. So its a 2 fold system.. EVEN IF u put a guage on it.. if its low, u have to replace one or the other & then if that doesn't do it, u replace BOTH.. Hope that helps.
The A25C has a wing mounted fuel tank plus a rear of cab high mounted boost tank, if the tanks are filled up you will not have any Sucking air issues, it is common to find faulty lift pumps on these engines but they still manage to run well enough, the Alpha drive can be something to check plus the torque stall speed will give you good information on the engine condition, a few air bubbles in the filter bowl would not be your running problem, your looking in the wrong place if it starts, revs and sounds good. tctractors
So I did some testing with a fuel can today, and feeding the pump with another can didn't do anything to help the air bubbles, but what I did notice was that the pump consumes a lot of fuel. I ran the truck for maybe 2-3 minutes and it sucked a lot of fuel out of the can. This caused so much return fuel to be sent into the bottom tank (which was practically full) to finish filling it all the way and caused fuel to shoot out the feed line. Is this normal for the pumps on these to have such a large amount of return fuel.
So if the valve is good will the pressure at the bleed port on the filters, where my book says to take fuel pressure readings, be somewhat consistant?
What is the Alpha drive, and what do you mean by torque stall speed? The truck starts good and sound good but it revs up real slowly, and when you try to drive it it just acts like it has no power.
Can you do a stall test and give us the max RPM you've got. should be between 1850-1950 rpm
Dakotab, its not intended to sound bad but you are somewhat flogging a dead horse worrying about a few bubbles in you jar, the rear fuel tank is 2 feet higher than your engine, the alpha drive is the bit in front of the injector pump that drives your pump, its an advance - retard injection control oil pressure fed, to stall test your torque you need to stuff it in gear 2nd or 3rd and stall the drive via the foot brake or up against resistance then stuff your boot into the throttle and note the rev speed, then under no load note the high idle speed, then post here but no half baked crap like " Around or Nearly" but the correct data. tctractors. p.s. How many up-shifts will the G/Box make on a clear flat road? does the Torque lock in the low gears? is the drop box in high or low?
Will just putting the gear selector in to 2nd or 3rd gear positions from a stop be ok to stall test the truck? I cannot get the truck to accerate past 5 mph even on a level surface, when you try to accelerate the truck just barely moves along and has no power. It has so little power that on slightly muddy ground, where it sunk in a bit, the truck had to be pulled out by a tractor.
Yes. You need to do 2 tests: - 1. With the transmission in neutral and park brake on, accelerate the engine to full throttle - note the maximum RPM. 2. Release the park brake, put your left foot on the service brake, and put the transmission into 2nd or 3rd gear. Floor the throttle with your right foot - note the maximum RPM. Post those two numbers back here.
Does anyone know what pressure the overflow valve should open at, I decided before I did the stall test I would check it, also will the valve always leak some? I tested it with air and a regulator and it opened around 12-15 psi. ( Sorry for the gap but the regulator I have isn't the most precise)
1.5 bar..== 21 psi..
Hi all. I am really late to this party but I had this problem a few years back with an A25c. Looking in from the front of the engine there are two air solenoids under the right hand side of the windscreen. One of mine stuck in an open position sending an air supply down to the trans retarder. These trucks don’t need to be in gear for the trans retarder to work. The truck would hardly shift out of first. Disconnect the air supply temporarily to these valve and let us know. I have a thread here somewhere about rebuilding that truck that goes through it all?
Do both solenoids work the trans retarder?
Ya one for each power level (one does 1st gear & overheat and the second full power retardation). Take away the feeding air supply and let us know?
I did bring up the retarder question in post 57 but air bubbles sort of blocked any interest, tctractors
Ok so a bunch of info on the situation so here goes. I put on the new overflow valve I talked about earlier, this made a little difference, the truck now accelerates ok in park from idle to about 1000 rpm, and decent from 2000-2400 rpm. I did a stall test on the truck and the highest it would rev is 900 rpm. The trucks max rpm is 2400. (Is this high enough it doesn't go into the red until 2800). I unhooked the air line going to the retarder, this didn't seem to make any difference in neutral. I found out the transfer case sensor is unhooked. That all said I did try driving the truck around, and the truck actually drove better, it would actually rev up to about 2200 rpm and I was able to get it to shift into 2nd. Any ideas on the best course of action?
Also I did notice the Aneroid covers have been off, and I'm wondering if someone messed with the adjuster. Does anybody know how to get the, what look like, headless screws out of the covers?
High idle speed should be 2600-2720rpm. 2400 is to low
Should the governor be adjusted higher then, or would adjusting the Aneroid be better first.
EVERY ONE I've ever done, the aneroid HAD to be adjusted for faster {lower} boost.. IF u can somehow get a boost guage inline, that would tell u which one first.. OR u can TRY to adjust the speed at the throttle stopper bolt.. JUST REMEMBER, THAT stopper bolt will only get u "so far" & THEN CUT THE SPEED BACK if u went TO FAR..
You have checked the Load Monitor control off the throttle arm to see it's within the datum lines?? tctractors
Yay !!!! Tony (tctractors) is back and helping again. Actually a couple of weeks now. I sure missed reading his comments.
I checked it and it is good, assuming the sensor itself is good.
Check the load sensor is working correctly. see attachment.
It looks like it’s been a while since this thread had any activity, but I’ll renew it by asking if anyone knows where to source a fuel gauge for an older A25C? Not available from Volvo. The gauge is a 24 volt unit, of course, and the hole in the dash is 2 5/8 inches. I performed the tests to ascertain that it’s the gauge and not the sending unit. This simple procedure was on the VDO website in addition to being fairly common knowledge. The sending unit appears to be at 90 ohms with the tank full. I can’t take it out to test it because the tank behind the cab is full. So I’m assuming that the sending unit range is 0 empty and 90 full. I did check continuity on the sending wire to the gauge and it is intact. The ohms reading at the gauge is 80 ohms instead of 90, but I’m guessing that there is supposed to be a difference there because of the length of wire would give more resistance?? I’m not competent on understanding ohms and resistance and that sort of stuff by any means. So if I could just find an aftermarket fuel gauge with the correct specs, even if it was the wrong diameter I could make it work. Any ideas? No luck googling it, so far.
https://www.amazon.com/VDO-A2C53412988-S-Fuel-Gauge/dp/B00T9LKL96
Also, thanks to everyone for the information contained in this thread. I hope the OP got his truck running right and shifting out now. I’m actually in a similar situation with mine, because the throttle cable broke and Volvo sent me a new one but we just stuck it in there with no instructions and then the truck wouldn’t rev up enough to shift on out. We finished the job with this old truck just poking around, but now I’ve got it back to my shop and I’m fixing everything that I can find wrong with it. One thing I’ve done is installed all new throttle cable parts, including a foot pedal and the levers on the injection pump so that there is no slack in any linkage now. $1,000 worth of parts, but it has to have correct rpms, I know. After I get the AC evaporator and heater core cleaned nicely and stuck back in there, as well as the fuel gauge and some other wiring issues in the dash and side panel done, I’ll install the steering wheel, seat, and floorboards and take it for a test run. I’ve no doubt it will shift if I get the rpms right, because it was shifting fine before the initial throttle cable failure. The only thing that I might not repair is the two speed selector. I think I read on here that’s for the Dropbox. Mine is stuck in either hi or lo, I don’t know which. But for the almost two years that I’ve owned the truck whatever range it’s in seems to work fine on my jobs. Not as fine as the new A40G I rented last job, but i paid more rent in two months than I paid total for my old A25C.
That’s a 240-33 ohm gauge, not a 90-0. But thanks for looking anyway.
https://www.google.com/shopping/pro...407022197,prmr:1,pid:5089817628407022197,cs:1 I guess I was saying, Google is yer bud, bud. The link above is what yer after
I've got a couple of genuine good used ones here if you can't find anything closer.