5.7 Starting Issue

[Slime]

So, my truck sat for several months ( I do that sometimes to dry the car ) Ran out the 3/4 of a tank of fuel that I had treated with stabilizer. Filled up with fresh regular, drove it home and parked it on a Friday. Tried to dive it that Sunday, but it would not start. I figured it was a fuel filter or pump issue ( it would crank and crank, sometimes acting like it might hit but did not ) Replaced the fuel filter, but tried to crank it after I had loosen the fuel line and it fired. Replaced the filter and it was fine. Then, 2 days later, same issue1 WTF? Cranked and cranked then several minutes later it started. No issues when driving it. So, I assume there is a check valve in the system. If so, where is it? Doesn't when you turn the truck to ON it just pressurize the system? Truck is a 1996 5.7 2WD with almost 180,000 miles. I replaced the factory fuel pump in 2010 and have had no issues until now. Now, I'm making sure to start it during every 24 hour period. Do I need to just replace the fuel pump assembly? Other than that, I have had no issues with this vehicle...ever!

 

[wheelman]

That 5.7 is a 350 R V8 they have that spider system fuel injection ..they got to have that steady fuel pressure.or it's not going to crank and run.if you could guage it.like the dealer does.it should be at 60 lbs.steady sixty.

 

[mars2878]

any updates?

 

[Slime]

Well, I thought starting it very day might help the problem. It seemed to work...until this weekend. Went out to start it Monday...same issue. Turns over, but doesn't start. Every once in a while during the process, it will act like it might start but doesn't. Then, after several minutes of this, on and off trying to start it, it starts and runs fine. I guess I need to start with the fuel pressure and see what it is. Where is the test plug on the fuel system? Or someplace to tap into. Do the average parts store have loner testers for that. I don't think I have one..

 

[Willyp926]

Try smacking the fuel tank with a rubber mallet or dead blow hammer when the problem occurs (I've had a lot of success with this) if it fires right up afterwards... then it would be safe to assume your pump is the culprit. Another way to check is to attach a fuel pressure gauge one night... wait until morning... turn the key and see where the pressure jumps to. If it doesn't move smack, the tank and cycle the key. Hope that helps

 

[Willyp926]

There's two fuel lines coming up from the rear of the engine, the larger one (supply line) has a test fitting on it, right behind the throttle body. A fuel pressure test gauge is pretty cheap last time I bought one.

 

[Supercharged111]

You can just rent the gauge. Last I checked mine was in Blow Reilly's parking lot. I think mine idled around 54psi and when I cracked the throttle it spiked to 60 or 62. Can also check and see if the pressure nose doves after you shut it down. That's about all there is to it.

 

[Slime]

It's a fuel issue. It had been fine until Monday morning ( go figure as I'm try to go to work) It's been raining here, so I haven't been able to check if it's the pump or a ground issue. I "Bled" the fuel line to see if I had pressure.... No pressure with the switch on. If it drys out tomorrow, I'll test the electrical stuff.

 

[Slime]

Okay...so I tested pins under the fuel pump relay as per this video

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On pin 85 (which is from the PCM) I got no voltage. So, I jumped pin 87 and pin 30 as per the video and I could hear the fuel line pressurize. No gauge, but you could hear it. I put the relay back in and the truck starts and runs. Tried a couple of times, still works...which is the issue I have. Sometimes it works, sometimes not...thoughts?

 

[Slime]

Same pattern today. went out Sunday and no start. Monday morning, because my car is dead i try to start the truck...same thing. So, i pull the relay and jump the #30 to the #87 pin. I hear the line pressurize . reinstall the relay and start the truck. Drove to work. Drove it home, even stopped at the store...still starts. I thought it might be the relay, but everybody says relays either work, or they don't....no sometimes.