Slight misfire and loss of fuel delivery - Ford Powerstroke Diesel Forum
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Old 01-30-2011, 07:24 AM
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Slight misfire and loss of fuel delivery

Hey guys, I though I would share this most recent repair with you all b/c of the complexity of the diagnosis and direction the repair went. I had a 2005 F550 w/6.0LPSD w/dump body on the back and 57K miles. Customer complained of fuel loss and stalling. The customers own personal truck mechanic brought me the truck after picking the truck upfrom another diesel shop and they diagnosed it as needing 8 injectors, fuel pump module and an FICM.
Symptoms: Truck starts perfect, idles for several hours with no problem, plenty of power but slightly less than 100%, no overheating, slight imbalance of power while idling, but no dead misfires. Engine would run mint for 1/2 mile under full acceleration and then lose power rapidly, seaming like each injector was cutting out 1 by 1. If the truck was driven causualy, it would go bout 2-3 miles before the same 1 by 1 injector drop out would occur under acceleration. The truck would start again after cycling key a few times and cranking over. There were many codes present for all 8 injectors, a few glow plugs, loss of signal for CKP sensor and a few other DTCs. I believed this to be from the many hands "playing" with the components and controls.

Diagnosis: Cleared the codes and drove it only to have a few injector codes and GP codes return. Additionally, if the cap on the secondary fuel filter or any joint in the fuel system were removed, a burst of pressure would spray out. More pressure then the max of 45psi that the system should ever see. Obviously, something was pressurizng the fuel system beyond the fuel pump. I tested a few other things and replaced the fuel filters only to find they were fine, but did so simply to satsify my suspicions. The one code that caught my attention was a performance code for inj #1, b/c the others were not performance codes, but resistance and so on. Using a temp gun, I checked that cyl #1 was infact not reaching the same temps the others were.

Repair: Replaced injector #1 finding no visible damage to the copper washer, injector seat, orings or the inj body. Reassembled and test drove. Truck ran great for a mile or so, but a misfire indicated on cyl # 5. Fuel loss and stalling ceased and did not occur after 10 miles of driving. R/R inj #5. Reassembled and test drove for another 5 miles. Truck ran like an SOB. Trouble was fixed.

I hope this will help others with the same problem. Apparently, if an injector fails, depending on the nature of the failure, the injector can allow compression to be introduced into the fuel supply backwards from the injector nozzle. This in turn overcomes the delivery pressure and starves the injectors of fuel. The most important features to keep in mind, are the extremely high pressure in the fuel system and the accompanying misfire. BE CAREFUL! The pressure in the fuel system overcame the check valves (did not damage them apparently). This was extremely dangerous b/c the burst out of the secondary fuel filter housing was like a water balloon popping w/less volume in the spray! This can catch you off guard espcially if your not wearing safety glasses (as you should while working w/any pressures).
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Old 01-30-2011, 08:19 AM
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There is a tsb that addresses this issue. The easiest way to test for this is to remove the secondary fuel filter and then cycle the key to fill the bowl up to the top. Unhook the fuel pump and then have someone crank it over and watch for bubbles. If you see bubbles then you remove the lines to the cylinder heads from the bowl and zip tie a rubber glove or balloon on the line and crank it over again and watch for the glove to pulse. Then remove the glow plugs on the affected bank and reinsert one glow plug at a time and crank it again and watch for pulses.
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Old 01-30-2011, 01:34 PM
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So Im guessing when these injectors fail in such an open state, they do not always set a code? I have replaced several failed injectors on the 6.0L PSD and I havent come across this compression in the fuel issue before. Only reason I stated this, was if the injector set a DTC for performance and compression was entering the fuel, one would not have to go through the isolation diagnostics w/ the glove (which is very clever BTW). As a shop owner, so long as the diagnostic procedure was accurate, I would want to approach the trouble with the most efficient means possible to reduce shop time and customer downtime. I would hate to have to gain access to each glow plug on these things to test the cylinders if I didnt have to. Man, its freakin tight in there!
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Old 01-30-2011, 04:17 PM
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The reason for doing the test as laid out in the tsb is that sometimes you get several injectors in one bank that are cutting out from one bad injector. It also states that if you have a burned copper washer you are supposed to replace the hold down for that injector as well. The glow plugs come out very easily if you remove the inner fender on the right side.
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Old 01-31-2011, 04:23 AM
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Thanks for the info bud. That makes perfect sense. BTW, you want a job? LOL. Have a great day man.
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Old 01-31-2011, 05:46 PM
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Too bad your a ways away or I may just think about taking you up on that offer. But there are a lot of great techs on here who would have told you the same thing.
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Old 02-05-2011, 09:01 AM
DPW DPW is offline
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I have cylinder 1,3,5,7 putting little to no rpm change at 1100 rpm
cylinder 2,4,6,8 rpm change about 200+ at 1100 rpm
fuel 51psi only code was for cylinder 1,5 out put but it changed from 1 or 5 or no codes
at all could 1 injector bad kill all
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Old 02-10-2011, 04:31 PM
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Quote:
Originally Posted by DPW View Post
I have cylinder 1,3,5,7 putting little to no rpm change at 1100 rpm
cylinder 2,4,6,8 rpm change about 200+ at 1100 rpm
fuel 51psi only code was for cylinder 1,5 out put but it changed from 1 or 5 or no codes
at all could 1 injector bad kill all
HUH? If you have combustion gasses entering the fuel rail then it can kill the whole bank, but there are also a bunch of other things that can kill injectors.
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