Engine/Transmission (1998.5 - 2002) Cold Start

[Wolfgang]

I have posted this before but here we go again.



My truck does not want to start after it sits for 30 minutes or more. Things replaced.

Lift pump (I did the lift pump last weekend)

Fuel line from gas tank to lift pump (Performed by dealer twice)

Roll Over valve on gas tank (performed by dealer)



Two weeks before the problem started the dealer had replaced the lift pump and I had installed a set of DD'2s.



If anyone has any other suggestions I really could use them.

 

[Wolfgang]

One other thing I haven't mentioned is it seems to start fine if it is pointed down hill. I went back and read some old posts on a return valve possibly causing this problem. Does anyone have a thought on this and where it is and what it looks like

 

[cam4g63]

Overflow valve

Looking at the factory service manual, the overflow valve is what maintains low pressure as delivered by the lift pump. The failure of this valve could cause the problem you are describing? If you look at the VP-44 from the driver's side fender, it will have two fittings facing you, with the rearmost one being the schrader valve for pressure tests (fuel supply line). The forward one is the overflow valve (fuel return line). If you had a pressure gauge hooked up to the schrader and an open or defective overflow valve, you would see it bleed off on engine shutdown, and perhaps a slow rise on start up. Try bumping the starter briefly and listen for the lift pump. If you wait 15 seconds, and then try starting the motor, and do not have any troubles, this may indicate that the fuel supply line to the VP-44 is losing pressure through the overflow valve - either that or you're lift pump is bad. Needless to say, verify that the fuel filter is good if you haven't done that already.

 

[Wolfgang]

The lift pump and filter has been replaced. Bumping the starter and letting the lift pump run doesn't help. I will try the test you recommended though and maybe pull that valve just in case. I do have one strange thing going on and that is my fuel pressure at the VP 44 is 3 WOT but before the filter it is 8 WOT. I don't know what this may indicate. Anybody have any ideas

 

[jaughenbaugh]

Hey, I think I know the answer to your problem. I just fixed it on my truck today. After changing multiple parts in my fuel system and having the computer re-flashed, this is what I came up with. The $37 dollar crank shaft position sensor was bad. This is located behind the starter in the block and all you need to do to replace it is pull the starter and take the 10mm bolt out and pull it out, unhook, re-hook and slide the new crank sensor in. I have been fighting this for a few months now and was almost ready to put an injection pump on. The reason that it probably starts when on a hill is that you get the hot oil away from the sensor allowing it to cool faster.

Let me know but I bet this will solve your problem.

Jim Aughenbaugh

98. 5 cab/chassis 3500, K&N, Edge EZ, Straight pipe, 100 hp injectors soon