Repeat #7 injector failure.

deezul · February 10, 2011

I have an 06 Econline that had previously had all four injectors replaced on the right head (1,3,5 and #7 which was stuck open allowing compression gasses into fuel system). Discovered that injector #7 had been improperly torqued from the factory (FQR) as when I removed it to replace it (the first time) the copper washer had been burnt off the injector as well as the lower o-ring. I cleaned the injector cup and inspected it with a borescope but could not find any issues with it. I then replaced the hold down clamp and fuel feed banjo bolt and finished the job. Truck has ran fine for the customer for the last couple of weeks. This afternoon the truck came back to me with the same issues. When I went to start it, hydrolocked. Scanned for codes, cylinder contribution codes 1,2,3,4,6,7 were all present. Removed glow plugs and cranked. Cylinder #7 was completely full of fuel. I'm going to tear into it tomorrow but do you think that the cup has failed? What are the chances of repeat injector failure(on the same cylinder as before)?.

(Fuel pressure isn't an issue 45 PSI at Upper Fuel Bowl)

lmorris · February 10, 2011

When you say 45PSI, is that underload?

There is a kit available with a valve that can simulate full load fuel flow when testing at an idle. 45 PSI is low enough to fail.

If 45 PSI is your no-load reading, it is possible that #7 injector maybe starving for fuel under load, thus causing a failure.

Keith Browning · February 10, 2011

If the injector was loose, has loosened... the copper gasket was burnt or pounded away the injector cup is almost always bad. Replace it and verify that your injector hold down clamp is the correct part.

Brad Clayton · February 10, 2011

Fuel pressure specs are a tad lower for E-boxes. It can go all the way down to 38 psi at the head and be "ok".

joshbuys · February 10, 2011

Fuel pressure specs are a tad lower for E-boxes. It can go all the way down to 38 psi at the head and be "ok".

That's correct because workshop has you checking fuel pressure at the back of the heads on an E-van, but if you're checking at the secondary fuel filter like on an F-series, the proper pressure is still >= 45 psi at WOT.

I cannot emphasize using the supplied 6.0L Diesel Fuel Flow Tester (310-193) enough, it's so quick and easy to set up, and gives you accurate readings, and allows you to see WOT pressures without having to put a load on the engine!!

deezul · February 10, 2011

Re-verified fuel pressure. It hangs around 40 psi at wot(simulation) using flow tester. Once again the injectors lower copper o-ring has been blown off as well as the lower fuel o-ring has been burnt. Cleaned the injector cup and inspected for wear, none seen but it will get replaced. Injector hold down was correct, checked torque on the other injector hold downs and all are torqued properly. This is the first time I have had repeat failure due to this reason...