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Service Throttle Soon and codes....

D

D2 Cat

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Location
south of Kansas City
Lately truck seems to pulsate in RPM's without me changing the accelerator peddle. Just enough to notice it. I though maybe fuel filter needs serviced, but I think it only has 5000 miles or so on it. Then I thought PMD acting up.

Then I checked codes.
23 (accelerator Pedal Position 1 Circuit range Fault),
31(EGR control Pressure)
32(EGR Circuit Error),
35(Injector Pulse Width Error-time short),
36(Injector Pulse Width Error-time long)
and 85 (don't know what this one is).

Yesterday the truck started fine, but for about 10 miles it acted like I might eventually get stranded by the way it was letting up and then catching on again. Speeds were various all the time, but up to 65 MPH. At about 10 miles down the road it seemed to clear up. I went another 12 miles and turned it off. Two hours latter it started right up ran w/o the stumbling for 5 miles. I stopped at the car wash and after that it went into another episode of stumbling. I got home OK, but I need to determine the cause.

I have a back up PMD which I am going to plug in. And, probably get a new fuel filter just because.....

Any ideas of where to start?
 
Clean every ground, batteries, motor and chassis straps.

Put a clear hose on the return fuel line and check for air bubbles.

The stumbling could very well be your PMD, you said you were going to swap it out so that's a good start.
 
Not the PMD.

Can the OPS fail to send power to LP "sometimes", or is it an all or nothing connection? I opened the WIF valve with engine running and NO fuel comes out. I open the cap at the filter an sometimes fuel comes out, one time I removed the cap and no fuel.

I thing the FP may be toast. But I'm also wondering if the OPS is functioning intermittently. If OPS fails will OP gauge show "0" ?

If I don't get it figured out before this snow comes in and I need the plow I am going to run a wire from Bat. + to OBD pin "F" to see if it runs smooth by my coaching!!
 
Run the power to pin F just to rule out the LP

The OPS part that powers the LP can go bad but the side that reads oil pressure still works.
 
This is VERY common on the non-OBD2 vehicles because the OPS sucks. There is no good option but to not use it as the power source, but you can still use it as the switch, and have it power a relay coil of a relay that sends power to the LP. This is a must modification on OBD1 trucks.
 
Update.
Possible causes of this hesitation, stumbling, now power, stalling: Bad LP, Bad OPS, Bad fuel, Bad PMD, air intrusion, or Bad IP.

When I jumper B+ to pin F the LP clicks. I open the Water Drain needle valve and very little fuel, sometimes no fuel. When I open the bleed screw on the fuel filter sometimes no fuel comes out. I have totally unscrewed the fitting and seen no fuel. I install a new Fuel Filter. Still stumbles after a while.

I install a different not new LP. Jumper B+ to pin F, pump click, open bleed screw, some air is expelled, then fuel. Disconnect my jumper and truck starts immediately. (All this is happening in 20 deg. to 6 deg. days) Last fuel was purchased from a Conoco Phillips station that sells more diesel then any other in this small town.

I push snow on 4 properties lasting about 1 1/2 hours. No troubles. No hesitation, runs fine. Next morning truck starts in 4 deg. weather at 6:30 am as soon a GP light goes out. I run truck until about 8:00 AM and I notice a stumble while driving 10MPH not pushing snow, just traveling through town. Make about 3 short pushes and stumbling becomes hesitation and I quickly realize I do not have the power to pull out on the street.

I set for about 15 minutes. Try starting truck and it fires right off. Seems to run fine. I finish to snow clearing for 10 minutes and drive 6 miles home with no trouble.

Truck sets for 2 hr. It starts without trouble. I push snow on two properties lasting 45 minutes and drive to the third place. Notice engine stumbles when coming up a short steep hill. Within 1/4 mile truck is hesitating, stumbling to the point I need to get off of the road so I won't be in someone's way. Truck idles at 400 RPM until it stumbles and quits.

I wait 1/2 hour. Hook up B+ to pin F. Bleed air from filter cap. truck starts right up. I push snow for 15 minutes. Truck begins stumbling and eventually dies again. Fifteen minutes latter I change out the PMD to another I know is good. I make the connection to pin F and truck starts right up. I remove more snow for 5 minutes. I leave the B+ to pin F as I work and drive off. Four miles latter it stumbles and I have to pull off the road. I don't wait. I just bleed the cap and check the WIF drain to check for water. No water. truck starts right up. I drive 2 miles and it does it all again. I'm home now and I'm done with this thing until tomorrow!!!!

As I type all this I'm thinking maybe my new FF is not sealing. What do you guys thing? I can't see the forest for the trees.
 
buddy, I sure thought I did when I installed it, but I'm beginning to question that. If I unscrew the top it probably won't seal correctly and I'll need a new one.

The one I just purchased is a different style then the one I took out. New one had a black plastic lid with a flat seal to set on the metal before inserting the filter assy. Is the old style NLA? 26 bucks for that thing makes me want a different set up.

I am thinking about removing it and starting over.
 
Is this the type that you dont have to use the plastic nut, it just has that incorporated as part of the filter? Those have been known not to seal properly for a few people anyway, and if there was an old gasket left from the old type it might not seal down on it. I bought a dozen of the old style at Rockauto a while back, $10 each.
 
You described it. I was sure the only gasket was the flat one that came with it. That gasket has to set on the flange just outside the riser with the slots of the fuel moniter. But at this point I feel like I fell of the turnip truck!
 
i would think if the filter lid ain't sealing good you got fuel pissing all over.
I would get a new OPS and while you'r at it put an extension hose between it and the block to get it out in the open and a new LP ,blow the line back to the tank to clear the junk from the sock and go from there.

Check the fuel suply hose at the firewall for cracks and being tight while you're back there for the OPS.
 
I installed a new fuel sending unit a few months ago. I removed the tank and made sure it was clean inside.

Bison, if I had a wire from the B+ to the F pin connected while driving wouldn't that over ride the possibility of the OPS having any impact on the stumbling----as long as it was hooked up directly? I've done that just trying to eliminate the OPS and after a couple of miles it goes through the stumbling, rough idles, quite mode just the same. This makes me think it's the new filter leaking or ......a crack in a hose at the firewall like you mention.

I replaced the hose from the FM to the IP and to the water separator valve and cleaned the FM at the time I did the FSU. Not much hose left to leak is there?
 
I had a terrible problem after changing my FSU. It was fine in the summer until it got cold.

TUrns out the replacement FSU had a GASOLINE sock on it, and didn't have the flap for the cold diesel fuel to get through. Reeked havoc all winter long. I had to blow air into the tank via LP inlet (fuel cap removed) ... I had to do this every 2 weeks until I took that sock off and installed a Racor Prefilter unit and fuel pressure gauge once and for all solved the issue.
 
D2 Cat said:
I installed a new fuel sending unit a few months ago. I removed the tank and made sure it was clean inside.

Bison, if I had a wire from the B+ to the F pin connected while driving wouldn't that over ride the possibility of the OPS having any impact on the stumbling----as long as it was hooked up directly? I've done that just trying to eliminate the OPS and after a couple of miles it goes through the stumbling, rough idles, quite mode just the same. This makes me think it's the new filter leaking or ......a crack in a hose at the firewall like you mention.

I replaced the hose from the FM to the IP and to the water separator valve and cleaned the FM at the time I did the FSU. Not much hose left to leak is there?
Click to expand...
Yes, that'll power the LP(btw how is your ground),but your LP could be crappy,good power to it wont change that.

Any leak post filter will piss fuel out unless the LP don't supply enough to satisfy the IP,then you get vacuum and air infiltration instead.(clear IP return tube will tell ye)

Matt might be on to some thing with the sock.
 
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