Fuel Issue! Sometimes NO START! Need advice.


Active Member
Oct 23, 2011
So I have searched the past threads and haven’t really found my particular issue, but I’ve read some good troubleshooting tips. Here’s what’s happening: Sometimes it will start right up sometimes it won’t start all all. When it’s cranking sometimes it will NOT register any fuel pressure on my gauge. Then when it actually wants to start then it will register around 40 psi. When driving and under boost it seems to work fine and rise 1:1 with boost. That’s what throws me for a loop because I would assume if it’s a week pump it would not be performing good when it’s running specifically under boost.

Today I hooked up a new fuel pump relay, it immediately primed when I turned the key to “ON” but then when I went to prime it two times after it did nothing.

I have eliminated some of the easier things, new fuel pump relay, it’s getting 12 volts at the relay and I also bypassed/tested the gray fuel pump wire and the pump did prime every time I hit the positive lead on the battery terminal from the gray wire.

Any other suggestions/advice would be awesome. I was going to drop the tank tomorrow to investigate some time. Thanks everyone!
Fuel pump or fuel pump relay could be going bad it's located on the passenger side fender
There are 2 relays located on that fender one is fuel pump and I honestly forget what the second one is
Is your oil pressure switch hooked up? If so it could be going bad . Most take out the sensor and replace it with a oil pressure gauge . Then you have to wire the oil sensor plug so it is bypassed .
Check out this diagram and you can see where all the fuel pumps power comes from
You have to wait a bit (10 seconds or so) between cranks for the priming circuit to reset.

And if the original oil pressure sending circuit is still wired and working properly after you crank the motor to over 4 psi. oil pressure the pump should run continuously with key ON in run and start positions.
I was helping a local friend with a very similar issue a few months ago. Here is what we found . . From memory . . .

The pump would prime, *sometimes*, and other times it wouldn't. FP was also low, *sometimes*.

Ran 12v to the prime connector. Sometimes the pump ran, other times it wouldn't. When it ran, FP was low *sometimes*. We verified battery voltage out of the HW relay (good when we did)

So now we have voltage but pump doesn't rum all the time. 2 different issues: Mechanical and possibly electrical.

Replaced pump. Hose was deteriorated (wrong hose) and pump was old.
Connection at the pump was also suspect. Replaced all that.

Problem now was it still primes sometimes and other times it doesn't . . . But FP is good when it does. 12V to prime wire and it runs most of the time. FP good.

Replaced stock relay at PS fender and good to go.

Take away:
A perfect storm that showed up when XFI was installed and clearly multiple issues.
If he has XFI, I know there is a 3-5 second delay from when you turn on the key to when you try to start it. If I try to start it without waiting it will not start and I have to turn the key off and start over.
If he has XFI, I know there is a 3-5 second delay from when you turn on the key to when you try to start it. If I try to start it without waiting it will not start and I have to turn the key off and start over.
Correct. It wouldn't consistently prime, even keying off and waiting 15 seconds. . . It was the perfect storm.
First thing first..

Note: the check engine light when the pump is not priming and the engine wont start.

If it does not come on when the key is turned to on position, the ECM is losing power. The fuel pump will not prime and the engine won't run. This can be due to a bad orange wire coming off the battery or a bad connection on the disconnect. Can also be from a bad connection or corrosion on the ecm plug. All scenarios can be intermittent. So don't rule it out because you see it on once. Always look for it. That and your volt light should be ON when the key is turned to on position.
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Thank you everyone. I will take all this info provided and try to diagnose the issue. I’ll chime back in if it runs any better. Much appreciated.

Side note: No XFI installed.
I was having the same issue as you , tried a new relay on the fender also did a new connector on the orange wire still had intermittent problems not priming the fuel rail so I unplugged the connector at the tank for my hotwire kit and plugged the stock one back in and never had a problem since [corrosion]
Update: Seems to be working ok after the new relay. I’m not sure if that was the real issue but hasn’t given me trouble since. Everything else checks out. Only things I didn’t do is drop the tank. That was my last resort. I’ll keep everyone updated if anything changes. Thanks again!