[CTDbrad]

My 1994 with 200k runs good when it's cold, but when it warms up and sits parked for a few minutes then it will act like it has vapor lock...spitting and sputtering....engine dying when I slow down...restarts and sputters until I get home. I have always gotten home so far, but sure was wondering.

I've done multiple configurations of fuel lines. I have 1/2" from the sump to the filter housing at this moment. No blockage at the sump. Extra venting of the tank. I've tried 5 mechanical fuel pumps...the original, 2 Chinese pumps, 1 used Carter of unknown miles and a brand new Precision brand pump manufactured in Israel. I've air pressure tested at least one configuration of fuel lines and I've used some reinforced clear vinyl to check for air intrusion. I'm reasonably confident that I'm not sucking air from the fuel lines. I tried a Holley Blue style electrical pump, at the tank, pushing fuel to the Israeli mechanical pump. Then I tried the electrical pump only...fuel pressure was about 10-16 psi with the electrical pump only. All of these combinations exhibited various levels of sputtering when warmed up. I could try an Air Dog or a FASS system next...but I think it would still have the problem. I also have a Tork tech overflow valve and a new FSS. Have I missed anything ?

Is it possible ? Do I have a bad Injection Pump ?

 

[dauntless89]

Try the cold water test. Dump a bucket of water on the injection pump when it's warm and doing it's sputtering thing. If the symptom goes away, your IP is the problem.

 

[CTDbrad]

Try the cold water test. Dump a bucket of water on the injection pump when it's warm and doing it's sputtering thing. If the symptom goes away, your IP is the problem.

Yes, I've seen that suggested somewhere. I think this cold/hot thing is already proven. When the injection pump is cold it runs good, when it's hot it tends to sputter. I should add this...the engine temp never seems to get over 170...so it's not overheating.
And I forgot to mention that one of the first things I did was to eliminate the troublesome fuel pre-heater.

I think I saw something about some of the 94 and 95 p7100 pumps having a defect, but I search and can't seem to find much information about this. I guess a call to an injection pump shop would be a good idea.

 

[dauntless89]

The earlier P7100s have a higher rate of sticking plungers in the bores.

Is the 170 from a gun or from the craptastic dash gauge?

 

[alanack6795]

Check fuel pressure, I had the same issue and it was low fuel pressure. The 94-95 pumps are especially sensitive to low fuel pressure. Replaced the OFV with a tork Tek adjustable and haven't had a problem in 50K when I was convinced my pump was toast.

 

[dauntless89]

Check fuel pressure, I had the same issue and it was low fuel pressure. The 94-95 pumps are especially sensitive to low fuel pressure. Replaced the OFV with a tork Tek adjustable and haven't had a problem in 50K when I was convinced my pump was toast.

In what way?

 

[alanack6795]

It's is my belief (speculation) that bad OFV roached most if not all of the 1994-1995s. Fuel flows cools the pump and the barrels warp when the pump gets hot. Low fuel pressure would make this worse on an already failure prone pump.

A lot of people can get by with a warped plunger/barrel leaving the tank the <1/2 full to help the pump run cooler.

Unrelated but a lot of performance guys complain about the cam in the 94-95 pumps, and higher pressure will help the slow fill cam.

 

[hemirunner426]

It was actually a tolerance change in the P&B in the later 160/175 pumps that largely rectified the issue. I bought my truck at 40k with a toast 160HP IP. It is a 94 built November of 93. My assumption is most early 160/175 pumps did not live long lives and were replaced. Others in cooler environments may of lived longer.

Ran like a top when cold. If you babied it it would run 30 minutes symptom free. Once it was heat soaked it would not run without pedal and it would spit and sputter like no other.

 

[CTDbrad]

Ran like a top when cold. If you babied it it would run 30 minutes symptom free. Once it was heat soaked it would not run without pedal and it would spit and sputter like no other.

This is what mine is doing. Drive perfectly about 10 miles to town, park and heat soak, and then spit and sputter home. Likes to go about 65 mph going home...if slowing down or stopping, it tends to die.

 

[CTDbrad]

I called a couple of Injection Pump repair shops, and both of them said to try a strong shot of lubricity additive in the fuel and see what that would do.
So, that's my next step. If that works, I'll keep doing it, if it doesn't, the p7100 comes off for a rebuild.

Who is the best at rebuilding these ?

 

[thor363]

I called a couple of Injection Pump repair shops, and both of them said to try a strong shot of lubricity additive in the fuel and see what that would do.
So, that's my next step. If that works, I'll keep doing it, if it doesn't, the p7100 comes off for a rebuild.

Who is the best at rebuilding these ?

Seth Farrell at Farrell Diesel Service, if you want it right and have the money.

 

[alanack6795]

Seth Farrell was also much cheaper than any other pump shop I called.

 

[GAmes]

I called a couple of Injection Pump repair shops, and both of them said to try a strong shot of lubricity additive in the fuel and see what that would do.

I doubt it will do anything, the claims far exceed the performance. But since you are going to I'd suggest Stanadyne. It works for the dry jet fuel the military uses in it's ground vehicles so it might work for you. Forget the internet myths about 2 cycle oil, it is a gasoline additive.

 

[9297oldram]

I doubt it will do anything, the claims far exceed the performance. But since you are going to I'd suggest Stanadyne. It works for the dry jet fuel the military uses in it's ground vehicles so it might work for you. Forget the internet myths about 2 cycle oil, it is a gasoline additive.

Just one man's opinion, adding lube would be worth it in your case might save on a rebuilt IP.

 

[GAmes]

Just one man's opinion, adding lube would be worth it in your case might save on a rebuilt IP.

https://www.thoroughbreddiesel.com/...dyne&utm_term=stanadyne&utm_content=Stanadyne

Stanadyne diesel fuel additives provides cold and hot weather protection; increase horsepower and improved fuel economy; lubricates and reduces wear of injectors and other critical components; cleans and prevents deposit buildup; reduces smoke and particulate emissions; helps remove water; fights rust and corrosion; and upgrades and stabilizes fuel, among other benefits.

I challenge you to find one 2 cycle oil maker that claims it lubricates diesel fuel components.

 

[alanack6795]

Dramatic sigh.

 

[CTDbrad]

Earlier today I poured about a half gallon of outboard 2 stroke oil, some chainsaw 2 stroke and some Stanadyne lubricity additive in the 1/4 full tank and went for a drive.

Heat is part of the issue and It was hot in west TN today. I drove a 10 mile loop and parked at a retail establishment to allow a heat soak. The truck ran almost perfect.
I think I heard only a very slight stutter at 2 slow downs to turn. It never tried to stall. So, I'm cautiously optimistic that some added lubricity may help the problem.

I was running the truck with the China made "Holley blue" imitation fuel pump only. It had about 8-10 psi fuel pressure at about 60mph, and about 15psi at slower speeds.
Is this fuel pressure OK ? The injection pump guy I talked to today said the pressure should be about 40 psi ! The factory manual on page 14-15 says that the factory overflow valve opens at 22 psi. I could try a Bosch 044 knockoff that I have at about 45 psi and see what that does.( Is that pressure too high ?) Or I could put the new Israeli mechanical pump back on.

 

[hemirunner426]

On a stock 160 you want approx 18 psi at idle and 25-30psi at 2000rpm no load. If you're at 15psi idle and are stock I'd say you're fine.

Fuel pressure isnt going to fix the problem though. A sticky plunger like what you discribe are not fixable in your garage.

Sent from my LG-H932 using Tapatalk

 

[dauntless89]

There's essentially no pressure attainable that's "too high." My pump has been running at least 25-35 psi at idle since I've had it.

 

[CTDbrad]

I found this partial description of p7100 operation-

"The fuel gallery is charged with low-pressure fuel (15 to 75 psi). This permits fuel to flow into and through the barrel ports when the plunger does not obstruct them. The plunger reciprocates within the barrel; it is loaded by spring pressure to ride its actuating cam profile. Therefore, the actual plunger stroke is constant."

Big fuel pressure range and I'm at the low end.