I have a 1987 Ford F800 dump truck with the 7.8l "Brazilian" motor. When I got it a few months ago, the speedometer did not work. I need to take my CDL test with it soon, and so I need to get the speedometer working. On the transmission output shaft there is a brass screw-in sensor with two wires coming out of it: a lime green one and a purplish-blueish wire. In the cab, the back of the speedometer has a 4 wire connector with 4 wires in it: two purplish-blueish wires, a lime green wire and a red wire with a stripe. Can someone tell me a test procedure to determine if the sensor or the speedometer itself is bad? This truck has a 5+2 manual transmission, so I assume that the red wire is the high/low signal wire and the lime green and purplish-blueish wires go from the speedometer to the transmission sensor. Is this true? In a related question, does anyone know where I can find a service manual for this truck? I've searched Amazon and nothing seems to be available. -Jon
on mine I had the same problem and I just ended up throwing parts at it and bought a Speedo sensor. I think it was around 40 bucks. That fixed my problem. does the speedometer move in high or low at all?
Not At All The speedometer doesn't move - and apparently, according to the previous owner, hasn't for at least the last 5 years.
There is a procedure for checking the sensor, take an ohmmeter and ohm across the sensor, there are two different sensors, I can't for the life of me remember what the spec on either sensor is suppose to be, but if you ohm across and end with nothing, or true continuty then the sensor is bad, i have in the past got lucky with unscrewing the sensor and wiping the end of it clean and reinstalling it. If it has not worked in five years I would replace it first, before I got into tracing wiring.
Congratulations, you have a rare truck that was seemingly sold in the US without any consideration for service and parts manuals by Ford. My professional opinion of these critters is exceptionally low. I've had the unfortunate circumstance of having to maintain two of these outcasts and neither one had any kind of manual available. The dealers I worked with did not have service or parts manuals either, but they did have parts microfiche. Parts were damn hard to get in any case for the cab and chassis. Engine and running gear was somewhat easier. I've never seen manuals for these trucks available anywhere else. It may be that others have had better luck than I have in this regard. I can't help with a test for the speedo system either. My only advice would be to sell the truck at the earliest opportunity and get something more maintainable. Good Luck!
I got manuals for my 89 f-800 with the 6.6L and a 5&2 off of ebay. My local ford TRUCK dealer is able to get me parts usually by the next day but most common parts are in stock. They sold the hell out of them parts are no problem. The Lucas girling juice brakes are a horrible horrible horrible system. but you can get parts their just $$$$$$$$$$$$$$. the truck I have the previous owner spent a tick over $7,000 for a brake job. Ebay for the manuals and a ford TRUCK dealer for parts. Fleet pride and other truck parts places can get most chassis parts. The engines are DAMN durable. mine has 7,100 hrs on it and never been opened up. its a boom truck so it sits and idles all day long then when its time to go home all 170HP is FLOORED! the Brazilian diesels are actually New Holland designs that use Bosch P pump injection. Their DEAD simple to work on. the only real problem I have with mine is rear ends. It eats them but I think that's more from me getting pissed at how slow it is and really hammering on it. I now use the low side for "In town" driving stop and go and just shift in to the "high" side when run out of gears on the highway.
Brakes Thankfully, my truck has air brakes - I've read that the juice brakes are a nightmare in the F-series trucks from this vintage. Does your manual say anything about the speedometer? I've set up an alert on eBay to look for the manual. Thanks for the tip.
Ok i will see about scaning the pages on the spedometer for you. I Dont have a scaner here so i need to sweet talk someone with a scanner to hook me up.
Wiring Diagrams I also have a fax machine if that works easier - (973)875-1617. Thank you very much!
Sensor Replacement Did Not Work I replaced the sensor on the tailshaft of the transmission. It was Ford part # E7H2-17B384-E and it cost $65.50. I was able to get it from Meadowlands Ford Truck sales in NJ. Unfortunately, this did not solve the problem. The speedometer is still dead as a doornail. I have not yet been able to obtain a service manual for this truck, so I still can't do any testing of the speedometer system. I guess I will next try swapping out the speedometer, but I hate to throw money and parts at this thing when it might be something as simple as a bad connection or wire...
Sorry Farious, I thought for sure it would be the speedometer sensor. have you checked to see if the red wire at the back of the speedo has 12 volts on it? As far as the wires coming off the sensor, check for continuity between the sensor and the speedo. Also, on the new sensor, did you install it correctly. Screw it in gently until it bottoms and back it out 1/2 turn?
Speedometer Installation The old sensor was very loose when I took it out, and was really gunked up on the end. I was sure that that the new sensor would fix the problem when I saw that. I put the sensor in until it was tight (but not over tight). I didn't back it out 1/2 turn. I will try backing the sensor out a bit and checking the red wire for 12v tomorrow and post the results back here. Thank you to everyone for help in tracking this problem down.
If you put it in tight, then drove it you might have ruined the sensor Check the ohms across the old one and the new one just to see what they read. If the end of the new one is ruined, clean the old one up, ohm it with an ohmmeter and try it again? Let us know what happens If the old one was loose and gunked up that could have been the problem all along.
Tests I did not drive it in tight, just snugged it up with a small wrench. I took out the new sensor today and took a look at it - it certainly had not bottomed out. The end was still in perfect condition, but had gunk on it. I wiped that off and reinstalled it. This time I put it in hand tight, and then backed it off 1/2 of a turn. I tried running the truck and the speedometer was still dead. I took the speedometer in the dash all of the way out. The plug in the back had 4 wires in it. When looking at it as if you were going to plug it into your mouth with the lock tab up, the wires were: black, lime green, black, and red with a yellow stripe. The leftmost black wire was 12v in high range, and 0v in low range. The rightmost red with a yellow stripe wire was 12v at all times. The sensor has lime green and black wires attached to it, so I assumed that the middle two wires were the sensor wires. I jumped them and ohmed the wires out at the sensor - I got about 1.5 ohms, so the wires have continuity. Just to make sure, I removed the jumper and the wires ohmed out at infinity, so I did get the right wires. I ohmed the new and old sensors. Both showed infinity. The speedometer is very complicated - it has a number of DIP switches on it and is a mass of electronics. It is part # "B E7HF-17282-AB" if anyone ever needs that information. At this point, that seems to be all that it could be. I will probably try to order a new speedometer on Monday and see if that fixes the problem. I did take a look at the circuit board briefly and it did not have anything obviously wrong - it didn't have an cracks, burned areas or blown-out parts. Hopefully I can still get the speedometer and hopefully that fixes the problem.
The dip switches are used to calibrate the speedo to the truck, you will need to set the new speedo the same as the old one, provided someone has not messed with the switches in the past.
Speedometer Not Available The speedometer is not available from Ford anymore. I had the part number wrong - the one I gave previously was an "engineering number". The real part number is "F1HZ17255C". I talked to FleetPride and Meadowlands Ford, and both reported the same thing. FleetPride is looking into whether an aftermarket speedometer is available or not. They said a square one is definitely not available (which is the style the truck has), but a round one might be. Hopefully one will be available and I'll be able to retrofit it into place.
Have you tried to locate a used one from a junkyard,Ebay, etc?
Junkyards I searched eBay and did a general Google search, with no luck. I'm new to the heavy-truck maintenance area, so I know of only 1 junkyard with bigger trucks, and he has an F800, but doesn't want to part out the interior because the truck only has a bad motor. I also have a friend who does electronics, so I'm going to pay him a visit this week and see if I can fix this speedometer at the component level. I'll try to get it working with a function generator and go from there.
Did you try calling HOOVER Truck in Netcong, you want to talk to Joe, he used to be parts mgr. at Condit Truck in Newton, he used to work at Turnpike Ford also, he is pretty sharp on that stuff. also IF SOMEONE changed trans and did not put rotor in [toothed ring] the pick up will not get signal, look in hole and see if it is in there. HOOVERS PHONE#347-4210
Latest Discovery I gave Joe a call at Hoovers (phone number 973-347-4210 in case anyone ever needs it) and he is a great guy. Unfortunately, he could not get the part, nor suggest anyone who could, although he did know of some companies that can repair the speedometer. I decided to take a look at the speedometer in more detail. I took it apart, and again did not find any burned or broken pieces. I put it back into the truck and tested the power. I wanted to see what type of signal was coming in on the signal wires, so I ran the truck with my meter on AC and didn't get anything. I tried DC and again, nothing. I tried on the frequency setting, and nothing. That was strange. I took the sensor out of the truck and the end was magnetic. This means that it should self-induce a current when it is near a moving, but interrupted metallic object. I took a paint mixer like http://www.amazon.com/Shur-Line-06200C-Gallon-Paint-Mixer/dp/B00004Z4H5 and put it in my drill. It has a hexagonal shaft, and I ran that shaft by the end of the sensor. When I measured AC voltage, I was able to get about 1VAC. I then put the speedometer back in the truck. I had someone sit inside the cab and I ran the paint mixer past the sensor while it was hooked to the speedometer. It worked! The speedometer was alive! I was able to get it up to about 10mph with my hexagonal-shaft-mixer trick. I pulled out the drive shaft and pulled the tail end off of the transmission. What I found inside I took a picture of and attached to this posting. I guess that someone had swapped transmissions at some time in the past. What came out of the transmission looks like it should be for a cable-driven speedometer. On Monday, I will call around to see if I can find a regular sensor pickup piece (I'm not sure what it's called) for the output shaft of the transmission.
yes that piece is for a cable drive. you could try G&G Diesel in lafayette nj you will need the trans model number so they can find the toothed ring thier #579- 5221 you any relation to john or sid?
Speedometer Working - Almost I ordered the new speedometer rotor for the transmission, along with a tailshaft seal and a rear housing seal. The rotor was Ford part # FUL 21558, the tailshaft seal was part # FUL 4300119, and the rear housing seal was part # FUL 4300852. The parts were all Eaton Fuller parts, but I don't know the Eaton Fuller part numbers. I've attached pictues of the rotor to this post. Everything came in yesterday, and today I reassembled the transmission and driveshaft. I took the truck out onto the road, and the speedometer was alive! Unfortunately, the correct speed is not registered. It looks like the speedometer shows about double the correct speed. I didn't change any of the DIP switch settings when I had the speedometer out, so I think that the new rotor has a different number of notches on it, or the transmission in the truck was changed and the new one is geared differently than the old one, or a combination thereof. Does anyone know how the DIP switches on the speedometer head are calibrated?
did you get my e-mail I sent on the dip switches?
Setting the DIP Switches I tried to call Meadowlands Ford Truck Sales in NJ, but they were useless in helping me figure out the DIP switch settings for the speedometer, so here's and explanation of what I did to get it working correctly. The speedometer takes an AC waveform, along with the hi/low selector input as its inputs. The AC waveform is generated by pulses from the gear on the output shaft of the transmission. There is a 10 switch DIP package on the circuit board that acts as a multiplier to get the correct MPH reading. Essentially, one must figure out the number of pulses per mile, then multiply this by an internal fixed multiplier and then multiply again by the binary-encoded value of the DIP switch. (Check out http://calc.50x.eu/ for a binary-decimal converter) In equation form: MPH = PulsesPerMile * InternalMultiplier * DIPSwitchMultiplier Unfortunately, no one knew what the internal multiplier was, so I had to come up with a different method. Here's what I did: 1) Take the dash apart until you can easily access the speedo. You will need to be able to drive the truck with the dash apart. 2) Start at the leftmost switch (most significant bit) on the DIP switch - turn it on. 3) Run the truck and check it against a GPS unit. If the speed reads high, turn the leftmost switch off. If it reads low, keep it turned on. 4) Go on the the second from left switch - turn it on. 5) Run the truck. If the speed reads high, turn the second from left switch off. If it reads low, keep it turned on. 6) Continue on down the line until you have checked all of the switches. As you get toward the right switches (least significant bits), it will get harder and harder to determine whether you are high or low on speed. An alternative, more accurate method you could use is to run the truck for a few miles and check the odometer against a GPS odometer. If the truck odometer reads high, turn the switch off. If it reads low, keep it turned on. Interestingly, the hi/low gear ratio does not seem to be encoded in the DIP switch. Perhaps the hi/low gear spread is the same in all rear ends for these trucks?