Engine/Transmission (1994 - 1998) HELP!!! 12 Valve barely running!!

[Motorhead]

I have been helping a friend with his '95. It would all of the sudden start cutting cycilders and stall at a stop. Through advice on the site, I stretched the return valve spring on the inj pump and it ran fine. It acted up about 2 months later and I suggested that we replace the return valve and that fixed it... ..... SO I THOUGHT!!! It is up to its old problems again. ANYONE HAVE A CLUE???

Is there anything in the onboard control needle computer that could be acting up? This IS a Calif truck.

 

[bmoeller]

Have you gutted the cat? Could be plugged. Problems with the EGR setup?



How's the fuel pressure? Fuel filter? Bad rubber fuel lines? Lift pump? Fuel injection pump may need to taken to a pump shop.



Idle speed way too low?

 

[Joe G.]

The '95 CA truck does not have an EGR valve. That started Jan,1,'96 so the early '96 CA trucks don't have one either. No computer involved with engine operation.



You may have stretched the return spring too much. Gotta be careful with that. A new overflow valve should have taken care of that symptom.



Does it run ok if the RPM is up? If it does then the idle is probably too low.



A fuel pressure test is almost mandatory to get much farther.



You can check a few things but you are just easter egging in an attempt to stumble over the problem. Briefly clamp the return hose with some pliers. If the engine smooths out then the overflow valve may be bad. Don't hold the clamp very long. Remove the pre-filter and clean it. If it's stopped up that could cause it. Check the fuel hoses. If they look bad change them. Sometimes they will suck air before they actually start to leak. Shouldn't kill the engine even then. Just be hard to start. The fitting where the steel input line attaches to the pre-filter/fuel heater may be loose or bad. If it is there is an air leak in that fitting the lift pump kind of fizzles out and it runs like crud. There have been a lot of lift pumps changed when that fitting was actually the problem. Naturally, when the lift pump is changed that fitting has to be disconnected and reconnected. The electrical connector to the fuel heater may be leaking air. Same symptom as the input fitting. Has the fuel filter been changed since this problem started? Are there any fuel leaks? If so, where?

 

[PUMPERDUDE]

Check the shut down soleniod to make sure it retracting all the way. If it the original ,its probably has a rotten boot and sticky. Good luck.

 

[Motorhead]

Joe G, There is some kind of electrical hook up on the inj pump. My wifes '84 mercedes diesel had the same set-up... It somehow controls the fuel control rod in the inj pump... . some sort of smog thing. This thing runs fine then like a light switch, it runs crappy. It will stay that way then it will run ok again. I bought a new return valve from Cummins.

It runs crappy at ALL RPMs. The fuel filter was changed ... no help.

Yes... NO EGR on this truck.

I hate like Hell to think his inj pump is bad, He only has 96,000 mi on it and he is an old trucker so he has taken reasonable care of it.

I will ck those fittings. It just doesn't seem like fuel because the fuel or air leakage problems that I have experienced cause the engine to "Fade" on all cyls. This thing misses.



PUMPERDUDE, I will ck the boot on the fuel shut off solenoid... . GOOD thought!!



PLEASE KEEP THE IDEAS COMIN' Thanks!! Chris

 

[Joe G.]

The only electrical hook up on my '95 injection pump is the TPS on the linkage. I have the CA version of the '95. I also have the service manual for my truck. The P7100 pump is purely mechanical.



Do you know which cylinder is missing? If you do swap the injector with another and see if the problem moves. If it is missing then you need to look at the injection pump and injectors. Everything in the fuel system before the injection pump will affect all cylinders the same.

 

[Missouri Mule]

Would a bad delivery valve cause a miss?

Injector that won't open will cause a miss. Crack your injectors open and see if fuel is coming out (do one at a time).



Will a dirty injector cause a miss or just amke the engine run rough?

 

[Reb.B]

need to see what cylinder is missing. It could be broken DV seal in the pump. 94 and 95 had them. It could also be your rod on the fuel shut off going bad. Sometimes that or the linkage will fail and not pull the arm all the way up, and you will have low HP. You didn't tuen a barrel on the pump did you. Two nuts hold each barrel on the pump. If you did this the same symptoms will happen.

 

[Reb.B]

also the lift pump could be going out, bad hose on the lift pump sucking air, or fuel line right above the transmission going bad. Usually the truck won't want to start when these go bad. If you pressureize the tank, (5-10 psi) and disconnect the return line and the truck runs fine, then it is one of those problems

 

[Motorhead]

Reb. B... . We have not touched the inj pump delivery valves. If the DV seal was bad, would it be intermittent? Would it affect more than one cylinder?

We had the return line replaced a year ago.



THANKS TO ALL YOU GUYS providind wonderful information and ideas. It is VERY frustrating trying to find a problem in a simple system.



I'll keep looking

 

[Joe G.]

Originally posted by Motorhead

It is VERY frustrating trying to find a problem in a simple system.

Yeah, this is 1940s technology. I had a small commercial fish boat with a WWII surplus 4 cylinder Buda diesel. It had an in line Bosch pump that looked just like a P7100. Different type of governor of course because it was mariine, but it worked the same way as our P7100 pumps.

 

[DMC]

Its about time the fuel lines be replaced, I would check the lift pump and the prefilter in the lift pump arrangement. Also get you friend to remove the fuel cap when this happens. You may be developing a vacuum on the tank. It sounds like a fuel starvation problem.



As far as the fuel shut of solenoid is concerned you can check this by turning the key on and manually push up on the rod at the base to see if it will hold the rod up. You can also check this with the engine running by making sure it is pulled all the way up.



Is this truck hard to start after sitting for a couple of hours?



The more details about this truck and maintenance you can provide the better.



Good Luck



Don

 

[T. Baker]

Sounds like air in the fuel to me. Anything before the lift pump leaking the slightest bit of air will airiate the fuel and cause problems. Start at the tank and check all fitting and hose clamps for tightness and continue up to the engine.

 

[DPyles]

truck shuts off

Yeah mine did the same thing ans I started throwing parts at it - overflow valve -two new fuel filters -fuel strainer and new rubber hoses at the bell housing and a new lift pump. Guess what . It still does it and I finally realized it would do it when on the fuel heavy going up hill it would start missing - bad - and if you took your foot off the gas it would just die. or when idleing for a long time it would shut off if the fuel level was under a quarter tank of fuel.

The one thing that never made sense to me after being on here and talking to these guys they all said it would be hard to start. This was never the problem as it started almost immediatly every time unless it was in one of it's spells. I never had a problem starting it even when it sat all weekend. It would just fire right up.

When the truck would go in to a fit I would pull off the side of the road and it would die as soon as I took my foot off the pedal. I would then get out open the hood and hit the fuel primer about thirty times or so. It would usually start right up and I was good to go for a while. I figure it has got to be the fuel pick-up in the tank. I had the bed off and inspected it and it was clean as a pin inside except for a very little bit of settlement but that is to be expected after about 160,000 miles on the clock. I could find nothing wrong or plugged on the fuel pick up in the tank but I now suspect that one of the hard plastic lines on the thing may be cracked and when the fuel gets below that point for a while it sucks air. ie; when idleing for a long time the fuel is not splashing around and going over the crack or when going up hill the fuel runs to the back of the tank away from the pick up unit.

One thing to note is that I had over a half tank of fuel when it did it the last time but I was going up an 11% grade for about 5 miles and when I got almost to the top in took a spell and I hit the primer and off I went.

Keep a watch on the fuel levels and the next time it does it let it die and prime the plunger seveal time and see if it fires up and is ok for a while.

One other thing, the truck also die while going down the 11% grade with my foot off the pedal for a while but fuel level was about quarter tank at that time.

Sorry this so long but I wanted to tell you exactly how mine is acting as compared to yours.

Hope this helps some.

Oh and if you need to check the pick-up unit in the tank I don't care what anyone says it is easier to tank the bed off than take the tank down. Had mine off and swinging in the garage in under 30 mins.

Let us know how this turns out.

I have not replaced the fuel pick-up yet $$$$$$$$about $250. 00 plus at the *******. I just keep the tank 3/4 to full.

 

[HCanales]

I spent hours trying to get mine running because it was doing the same thing you're discribing. I even took apart almost every fuel line on that fuel system, no luck! I put a new lift pump and it did the same thing! I knew the system was getting cavitation but where?

Like Joe G. said about the fuel heater, if the electrical connecter is not on connected properly it won't run well. You can pump the primer and it will run well for a short while but it will continue acting up. I also notice that there was no leaks, what a b--ch! Guess what? Fuel heater wont leak because its suckin the rubber gasket on the fuel heater connector to seal! I tested it with a vaccum pump to validate and sure enough it leaks air with out the rubber seal, what a retarded idea to seal a leak with a electrical connecter! but thats how it works.

Try that avenue and see how it works, good luck!

 

[Cooker]

If fuel leaks at the electrical connector on the fuel heater, the fuel heater needs to be replaced. The fuel heater is not supposed to leak at the connector and the gasket on the connector is meant to keep the dirt out and not the fuel in. I had the same problem with my fuel heater.



I will not be replacing my fuel heater again. The next time it is coming off completely.

 

[Joe G.]

You might try to pressurize the fuel heater/lift pump assembly in a bucket of water and see what happens. See page 49 of issue #44. That article has been edited quite a bit. I've been running mine without the fuel heater since I found the leaking connecton. Someone else did that test and found that the input fitting to the assembly was leaking.

 

[Motorhead]

AGAIN... . Thanks for any and all ideas. I am going to dive into this thing next week and ALL suggestions will be looked into.

Thanks Friends!!!! CHris