DIAGNOSING FUEL LEAKS

[TonyL]

I WAS HOPING SOME PEOPLE HAD SOME TIPS FOR FINING AIR LEAKS IN THE FUEL SYSTEM. I REMEMBER READING THAT YOU CAN PRESSURIZE THE TANK WITH A VALVE STEM IN THE FUEL CAP. IS THIS ACCURATE? THIS MAKES SENSE TO ME BUT WONT IT ONLY WORK UP TO THE LIFT PUMP? ALSO MY TRUCK HAS CLEAR TUBING ON THE INJECTOR RETURN LINES AND THERE ARE BUBBLES IN THEM WHATS THE BEST WAY TO DIAGNOSE THE PROBLEM?

THANKS

TONY

[britannic]

Pressurize the tank to around 7-10psi and then check the lines for leaks over the next 30 minutes. Pay special attention to the fuel filter housing if you have the FM80, since this is a major source of leaks. Another favorite spot for drawing in air is the flexible hose connection at the lift pump.

Leaks are easier to spot after the lift pump, as the fuel is now under pressure. The IP throttle shaft seal can leak fuel giving similar symptoms to a fuel line air leak.

The later mechanical lift pump uses vent free check valves to prevent drainback and the later IP return check valve incorporates an anti-drainback device as well. Drainback causes air leak style symptoms upon start up, but not when the truck is warmed up.

[TonyL]

so if i pressurize the tank that should allow me to dee any leaks up to the ip. How about the bubbles i have in the lines between injectors?

[britannic]

Anytime a lot of air gets into the IP housing it can cause weird running behavior. The IP vents air through the internal vent wire and out of the return check valve back into the tank. Any air present in the inj. return lines can be a sign of leaks somewhere in the system or in rare cases a faulty injector. IMHO, it's best to rule out the obvious sources of leaks first and then continue the search if it doesn't resolve running/starting problems.

Here's a thread that discusses how the IP works and explains the vent wire's function: How The DB2 Works (http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=2;t=002168)

[TonyL]

I was wondering about the injector return lines, the ones that go from injector to injector. I saw some on one of the advertisers web sites and thay have clamps on them. As i mentioned before mine were replaces with clear tubing and have no clamps is that some thime that should be taken care right a way.

Thanks
tony

[arveetek]

A lot of times the clamps get thrown away during service. As long as your return lines aren't leaking fuel, then they're okay for now.

If they start dripping fuel when the engine is running, then it would be a good time to replace them. You can buy a kit from some of the DP advertisers that come with new lines and clamps.

Casey

[britannic]

Originally posted by TonyL:
I was wondering about the injector return lines, the ones that go from injector to injector. I saw some on one of the advertisers web sites and thay have clamps on them. As i mentioned before mine were replaces with clear tubing and have no clamps is that some thime that should be taken care right a way.

Thanks
tony Keep an eye on those clear lines, they may not be up to handling diesel for any length of time. A return failure won't stop the engine, but it will waste fuel and create a dangerous situation if it ignited. Inj. Return line kits are available from DP advertizers like Kennedy Diesel.