Engine/Transmission (1994 - 1998) Fuel pressures

[hsmith]

I have been having intermittent hard starting problems. At times it seems like it is sucking air. New lines, filter, prefilter. This weekend it started fine, but after idleing for a few minutes it stalled and would only start and run for 10 seconds or so then die. Lucky for me we were in a RV park and not on the road. I carry a spare filter, so replaced it, primed and away we go. 220 miles hard pulling with no problems.

Started it this morning and made it two blocks and same thing. Thought I got some bad fuel, but saw no evidence of any. Now it starts, stumbles, then clears out. Also at idle, pressure fluxuates from 20 to 30, 15 to 25, etc. I am leaning toward weak lift pump, although everyone says they are very reliable.

So, what do you think?????? Also checked the ofv.



Smitty

 

[Dieseldemon]

Next time check the filter and if it is half full you are losing prime check the return line for a small leak.

 

[Joe G.]

Email me at -- email address removed -- for my write up on the 12 valve fuel supply system, how it works and how to fix it.

 

[hsmith]

I am good with all that part about the return line. The fluxuating pressures to me leads to pump failure.

 

[Joe G.]

I doubt that fluxuating pressures are going to bother a 12 valve lift pump because of the way they are made.

 

[Howard Durand]

If it starts and runs for a few seconds then dies, I would guess there is an air leak somewhere between the tank and the lift pump. There are a number of places where that can happen.

I have a "bad" lift pump in a box on the shelf that I replaced a couple of years ago which didn't solve the problem. After replacing the supply lines, making sure the lines fit the tubing, making sure the clamps were tight and uttering a few profanities, the problem went away.

I also had fluctuating fuel pressure which leveled out after I stretched the spring in the OF valve.

 

[JFaughn]

The LP are reliable , but that does not mean that they do not wear out / fail .
I took mine apart when I had some hard starting issues on a low tank .
found that the valves were coming apart .
Replaced & still did not have good fuel pressure , so after testing [ pinch fuel line / used OFV ] I put in a new overflow valve , most everyone thought it was the fuel lines / houses , to check that , I pressurized the fuel tank about 3 lbs , to look for fuel leaks from tank to lift pump [ normally this is a vacuum , so no fuel leak till theres pressure ] .
So to save money & fix right the 1st time , test & only replace what is bad .

 

[hsmith]

Making progress for sure. Cured the fluxuating pressures by cranking down the needle valve for the gauge some more.

Also found I could twist the rubber supply line at the clamps. Tightened the clamps and so far so good. Several weeks ago, I replaced both the rubber lines, and hope I failed to fully tighten the clamps enough. Will give it a few more days before I say it is fixed.

Thanks to all again.

 

[hsmith]

Just an update, I am sure tightening the hose clamps cured my problem. Must have been loose enough to lose prime.

Thanks for the help. Some times we have a hard time seeing the forest for the trees in the way.