5.8 Hard to Start
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Senior User
Joined: Jul 2006
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From: Eureka, KS
5.8 Hard to Start
Having fuel pressure issues and I can't pin down what's going on. checking fuel pressure I hardly get any with first turn of the key. Pump runs (either tank) but nearly no pressure. If I turn key on several times it will build up to like 40psi but not start every time even then.
If I jump the fuel pump over at the EEC test plug and run the pump constant it will fire right up.
Idle pressure is about 30psi. It will jump up when I hit the throttle and when I romove vac line from regulator.
Any ideas on what my problem is? When pump stops running the pressure drops near zero almost immediately.
Thanks
If I jump the fuel pump over at the EEC test plug and run the pump constant it will fire right up.
Idle pressure is about 30psi. It will jump up when I hit the throttle and when I romove vac line from regulator.
Any ideas on what my problem is? When pump stops running the pressure drops near zero almost immediately.
Thanks
Hotshot
Joined: Sep 2001
Posts: 11,958
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I had a very similar problem and it turned out to be that several of my injectors were bad. The pressure would leak down as soon as the engine was shut off.
I ende up replaceing them with 19# Ford Racing injectors from Summit for about 200 bucks. Jegs also has them. New ones from the parts store were at least 50 bucks each and Ford wanted almost 100 each.
Does your problem happen all the time or only when hot or cold etc? It could just be the fuel pressure regulator with has a vacuum port on it. It is located on the driver side rear of the fuel rail. Its an inexpensive part to replace and an easy task.
It could also be a bad fuel filter that is clogged up.
I doubt that both of the pumps are weak, so I would probably rule out bad fuel pumps.
I ende up replaceing them with 19# Ford Racing injectors from Summit for about 200 bucks. Jegs also has them. New ones from the parts store were at least 50 bucks each and Ford wanted almost 100 each.
Does your problem happen all the time or only when hot or cold etc? It could just be the fuel pressure regulator with has a vacuum port on it. It is located on the driver side rear of the fuel rail. Its an inexpensive part to replace and an easy task.
It could also be a bad fuel filter that is clogged up.
I doubt that both of the pumps are weak, so I would probably rule out bad fuel pumps.
Fleet Owner
Joined: Aug 2005
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From: Easton,Ks
Sounds like you have a bad check valve in one of your Fuel Delivery Modules (FDM) in one of your Fuel tanks.
You should also see that one of the fuel tanks, the one that you are not using is filling as you drive.
This is the one with the bad check valve.
You should also see that one of the fuel tanks, the one that you are not using is filling as you drive.
This is the one with the bad check valve.
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Senior User
Joined: Jul 2006
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From: Eureka, KS
Well I was thinking it was one of the FDM check valves but it doesn't appear to transfer fuel to either tank while driving.
If I'm seeing an immediate pressure drop after the pump shuts off at the fuel rail...wouldn't it have to be the FPR check valve or an injector/s?
It's just really confusing me. I'd like to slap on a new FPR but they're like $70. I do have at least one very ticky injector.
I've got my Haynes manual and the procedures for checking fuel pressure. I need to follow some of the instructions on isolating where the leak is.
I don't doubt something is worn out, it's got 200k miles on it.
The problem seems to be related to how long it sits after running. It does just die out of blue sometimes when I'm driving, usually not too long after I head out somewhere.
If I'm seeing an immediate pressure drop after the pump shuts off at the fuel rail...wouldn't it have to be the FPR check valve or an injector/s?
It's just really confusing me. I'd like to slap on a new FPR but they're like $70. I do have at least one very ticky injector.
I've got my Haynes manual and the procedures for checking fuel pressure. I need to follow some of the instructions on isolating where the leak is.
I don't doubt something is worn out, it's got 200k miles on it.
The problem seems to be related to how long it sits after running. It does just die out of blue sometimes when I'm driving, usually not too long after I head out somewhere.
Fleet Owner
Joined: Aug 2005
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From: Easton,Ks
If you always run on the tank with the bad check valve in the FDM then the other tank would not fill and it would act this way.
If it were the injectors always open I would think it to run very bad and smoke black when you start it.
Most of the time FPR do not fail this way, when they start to fail you will get fuel through the vacuum hose into the intake. If you pull the hose off of the nipple while it is running you should see fuel dripping out of the vacuum hose. If you see any fuel at all it is bad.
If it were the injectors always open I would think it to run very bad and smoke black when you start it.
Most of the time FPR do not fail this way, when they start to fail you will get fuel through the vacuum hose into the intake. If you pull the hose off of the nipple while it is running you should see fuel dripping out of the vacuum hose. If you see any fuel at all it is bad.
Fleet Owner
Joined: Aug 2005
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From: Easton,Ks
The fuel pressure should hold even with the FPR off its seat as the shuttle valves in both FDM should be closed. If one of the shuttle valves was stuck open you would still have one tank filling the other one as you drive.
But I would not think a leaky injector would drain the whole fuel system and that is what you are saying.
But I would not think a leaky injector would drain the whole fuel system and that is what you are saying.
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Fleet Owner
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From: Easton,Ks
All the Ford Shop manual says is:
Check injectors for leakage and flow rate, using Rotunda Injector Tester 113-00001 and Rotunda Fuel Pump Check Valve-Pressure Regulator and Injector Leakage Tool 113-00010, SBDS Injector Flow Tester or equivalent.
Does the system maintain fuel pressure and is flow rate for individual injectors within specification?
Yes
CHECK fuel lines for leaks. If OK, REPLACE fuel pump. RECONNECT all components. GO to «FDS2» for verification.
No
REPLACE the damaged injectors as required. RERUN test FDS14. REPEAT «FDS3».
Check injectors for leakage and flow rate, using Rotunda Injector Tester 113-00001 and Rotunda Fuel Pump Check Valve-Pressure Regulator and Injector Leakage Tool 113-00010, SBDS Injector Flow Tester or equivalent.
Does the system maintain fuel pressure and is flow rate for individual injectors within specification?
Yes
CHECK fuel lines for leaks. If OK, REPLACE fuel pump. RECONNECT all components. GO to «FDS2» for verification.
No
REPLACE the damaged injectors as required. RERUN test FDS14. REPEAT «FDS3».
Thread Starter
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Senior User
Joined: Jul 2006
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From: Eureka, KS
It's just getting worse. Harder to start, dying more often then hard to get back started. I'm kinda lost as to diagnosing the problem. For the cost to have shop find the problem and fix it I could just replace both FDM's, the FPR, filter, and injectors myself...that would cover pretty much everything, lol
With this type of fuel line on this truck it's very difficult to do the tests that are required.
So the system is sealed at the injectors and at the FDM's? It seems like since I get hardly any pressure when I 1st turn the key it would be in one of the FDM's, just because of gravity. The first prime would get the fuel volume back in there, next primes would build the pressure. Only bad thing is I see no signs of cross flow between tanks, which i would expect to see.
With this type of fuel line on this truck it's very difficult to do the tests that are required.
So the system is sealed at the injectors and at the FDM's? It seems like since I get hardly any pressure when I 1st turn the key it would be in one of the FDM's, just because of gravity. The first prime would get the fuel volume back in there, next primes would build the pressure. Only bad thing is I see no signs of cross flow between tanks, which i would expect to see.