I have been working on a friends truck for about a week now. The syptom is, sometimes it starts and runs perfect and sometimes it won't start at all. It does not depend on the time of day nor outside temperature. If it does start you can shut it off and crank it right back up with no problem at all. It will also never die on you once it is running.

What I've done is put a fuel pressure gauge on the fuel rail. The original fuel pump was only about 30 psi and if I zero the gauge out even while running it took about 30 second to build back up to 30 psi. So I replaced the fuel pump with a new Bosch fuel pump. It seem to run great for me. I would crank it about every hour or two and it always started right up. I thought it was fixed so I gbe it back to my friend. He called me the next day and said it wouldn't start. I got it back to my house and put the fuel gauge ban on it and discovered that when the truck would start the fuel was 48psi. When it wouldn't start it was 20psi. So I removed and replaced pump with another new Bosch fuel pump.

I drove it around all day yesterday and it started right up every time throughout the day. When I parked it for the night I let it sit for a couple hours. I went out to crank it about 10:00 and it would not start. I got my gauge out, hooked it up and fuel psi was at 4psi. I turned key switch off and back on again and fuel pressure didn't increase at all. I can hear the fuel pump running. So while the gauge was hooked up I just started cranking. The pressure slowly increased (1psi per second.) when it got around 30 psi it almost started. It finally go to 50psi and it fired right up.

So I am extremely confused. Can anyone please help.

 

It really sounds like you've got a shiat fuel pump again. Unless something is REALLY clogged between the tank and the fuel rail.
Are the pumps remanned?

Oh yeah, WELCOME TO DF!

 

I am not sure if it is new or a reman. It is $245 from advance auto-parts.com.

 

That's a new pump. I'm thinking the ASD relay or fuel pump relay . Try swapping relays around. You might also want to inspect , test or replace the coil wire and coil. Any chance it only does this when there is dew or raining ?

 

Hey can be anytime of day or any type of weather. I can't explain the low pressure when it won't start. It has pressure just not enough.

 

It could be the ASD shutting down due to bad wiring or a spark problem (which will also shut it down) . You have lots of thing's to troubleshoot. I highly doubt you got two bad pumps.

 

I forgot to mention earlier when it would crank but not start I did check to make sure it was getting spark. I took out the number 1 spark plug and it sparked every time piston puffed air out. So that tells me it has to be fuel related because I also had air filter off truck. All it needs is air, spark, fuel.

 

A nice blue spark or yellow?

 

It was a yellow spark. I wish I were blue but at least it did spark. Why would I be able to hear the fuel pump but only have 20 psi when it won't start?

 

Should I just buy a different brand fuel pump? I need to get this truck returned to owner. But I need to make sure it's fixed for sure this time. It's a horrible feeling to have a truck come back after you think it's fixed.