Need help

[Michael006]

I had fuel line replace to the filter new sending unit and LP installed. If the truck truck sits over night it starts in the morning. If I drive it work when I go to leave 8 hrs or so later the truck will stsrt and run for a couple of second and then lose fuel prime I can’t find fuel leaking anywhere. Any suggestions would be helpful.

 

[MrMarty51]

Hi Michael, welcome to the truck stop.
What kind of a truck are we working over here ?

 

[Michael006]

94 Chevy 3500 with 6.5 turbo diesel.

 

[Will L.]

Get clear tubing, 1/4” diameter X 6” long from any hardware store and a couple screw clamps to fit it.
Replace the rubber line coming out the front of the ip (injector pump).
Run the truck and watch for a trail bubbles. This indicates air intrusion from the tank to the lift pump, provided the lift pump is working. If the lift pump is not working it could be anywhere in the fuel line from tank to ip.

Running a jumper wire to the lift pump from the battery will have it run continuously. Do this and purge the ffm of air as if you just replaced filter.
After that turn key on, but do not start engine. Fuel should flow through the ip and through the clear tubing. Now watch for bubbles again. If no bubbles, start engine and watch again.

Loosing prime will almost always be because of leak in the system and if is before the pump, the pump will suck in air- not leak out fuel.

There is more to do after the air leak test if no bubbles are found- pressure test at the ip inlet fitting. But best to do one step at a time. Mod Mafia sells a fitting to go between the ip and the metal line where you tap the fuel pressure gauge. Best option is to permanently mount an electric fuel pressure gauge in the dash so you can always see it. Pressure should be 8-14 psi. Low pressure causes problems, no pressure wears out the ip really fast. Ordering the adapter now is a good idea imo. Some folks here might have found another source for that fitting, idk.

 

[Michael006]

Get clear tubing, 1/4” diameter X 6” long from any hardware store and a couple screw clamps to fit it.
Replace the rubber line coming out the front of the ip (injector pump).
Run the truck and watch for a trail bubbles. This indicates air intrusion from the tank to the lift pump, provided the lift pump is working. If the lift pump is not working it could be anywhere in the fuel line from tank to ip.

Running a jumper wire to the lift pump from the battery will have it run continuously. Do this and purge the ffm of air as if you just replaced filter.
After that turn key on, but do not start engine. Fuel should flow through the ip and through the clear tubing. Now watch for bubbles again. If no bubbles, start engine and watch again.

Loosing prime will almost always be because of leak in the system and if is before the pump, the pump will suck in air- not leak out fuel.

There is more to do after the air leak test if no bubbles are found- pressure test at the ip inlet fitting. But best to do one step at a time. Mod Mafia sells a fitting to go between the ip and the metal line where you tap the fuel pressure gauge. Best option is to permanently mount an electric fuel pressure gauge in the dash so you can always see it. Pressure should be 8-14 psi. Low pressure causes problems, no pressure wears out the ip really fast. Ordering the adapter now is a good idea imo. Some folks here might have found another source for that fitting, idk.

 

[Michael006]

So interesting thing happened I jump out LP without the engine running and all of a sudden fuel starting pouring out from about the bell house I’ve had all the fuel line replaced and return line the only other thing there is the fuel filter housing. I’m thinking it’s cracked is this a common problem???

 

[Big T]

So interesting thing happened I jump out LP without the engine running and all of a sudden fuel starting pouring out from about the bell house I’ve had all the fuel line replaced and return line the only other thing there is the fuel filter housing. I’m thinking it’s cracked is this a common problem???

1994 vintage all fuel lines, including the hard lines, are suspect. Also sending unit on tank and the tank itself. Just went through this on a ‘94. It’s worse for trucks in the rust belt.

 

[JMJNet]

The fuel filter canister (FFM) is also prone to leaking with age.
There are 2 o-rings but it can also leak from the area where the wire comes out.
The grommet on that wire hole is not replaceable.
I had replaced both o-rings and still leaking from that wire hole.

In my 95, I had to buy a complete new canister.
It is not too bad in terms of price.

You also need replace the 2 hoses to the IP and drain t-valve which goes under.
In my case, I bought M10-1.50 threaded rod, cut it to around 9.5" and use this to raise the FFM.
So, those 2 hoses run above the intake and easier to see if it leaks.
Besides, it is easier to connect those hoses above/outside the intake to the respective connectors.

 

[MrMarty51]

If needing the entire FFM, might be worth while to go to Leroy Diesel and buy his Feed The Beast kit. Also install the T fitting at the injection pump to get a fuel pressure gauge attached to the system too.
You wont be sorry for spending on those two uprated componemts.

 

[Will L.]

Yup. Something of the above mentioned parts is leaking.
Sae30r9 fuel line.
Still add the clear return line and the fuel pressure gauge once this is solved.

And I bet a dollar to a donut the gauge will prove to you that the lift pump is not putting out properly once because it leaked when engine off but not engine running so that means the ip was sucking fuel faster than the LP was suppling it.