'98 E-350 early build 7.3L

mchan68 · September 1, 2007

Helping a guy out on one that was towed in for a no-start. I advised him to replace all eight injector o-rings and an IPR valve. The truck now starts fine, but blows a lot of smoke even when warm. I went over to this place after work, and ran some self-tests. Injector Buzz Test: PASS. KOER On-Demand: PASS. KOER Cylinder Contribution Test: P02** codes for cyl. #1 and cyl. #2. I advised the guy to drive the truck home to see if the smoke clears. What do think? O-rings improperly installed? Or mechanical base engine issues. IPR duty cycle was 15 to 16% before repair (it was started with "love juice"). IPR duty cycle now at 13% at hot soak, after repair. Shouldn't it be between 9 to 11? Any possibility of a bad injector(s), even though it passes the buzz test? I don't have a 7.3L injector tester at my dealer.

Bruce Amacker · September 1, 2007

Helping a guy out on one that was towed in for a no-start. I advised him to replace all eight injector o-rings and an IPR valve. The truck now starts fine, but blows a lot of smoke even when warm.

What color smoke? I assume blue, but it could be white (misfire) if it's not running well.

I went over to this place after work, and ran some self-tests. Injector Buzz Test: PASS. KOER On-Demand: PASS. KOER Cylinder Contribution Test: P02** codes for cyl. #1 and cyl. #2.

It's running bad, right? White smoke from misfire?

I advised the guy to drive the truck home to see if the smoke clears. What do think? O-rings improperly installed?

I have seen a couple of times where the o-rings wore a groove into the cylinder head and still leaked after being replaced. Not common, but I thought I'd mention it. You could feel the groove with your finger and a new head fixed it both times.

Or mechanical base engine issues. IPR duty cycle was 15 to 16% before repair (it was started with "love juice"). IPR duty cycle now at 13% at hot soak, after repair. Still a bit high.

Let's go over the o-ring diag again: Upper o-ring leaks, hard start- extended crank, slow to build ICPV. Center o-ring leaks (with mechanical FP and return lines from the head to the FP regulator) causes oil to migrate into the fuel tank. Center o-ring leaks on a Gen2 system (electric FP, no return lines from the heads) causes smoking, because one head ends up running on engine oil rather than diesel fuel. If either the upper or center o-ring is leaking will cause elevated IPR command.

This is an early truck with mechanical fuel pump, right? If it is, it has return lines to the fuel tank. If the center o-ring on the injector was leaking, the fuel tank will be loaded with engine oil, hence your blue (?) smoke. If it's an electric fuel pump, it will not have return lines from the heads, so there should be no oil in the fuel tank.

Shouldn't it be between 9 to 11%?

Yes. If you think the upper o-ring s could be leaking, pull the VC off and visually inspect while idling. If they are leaking, there will be a geyser there. /forums/images/%%GRAEMLIN_URL%%/grin.gif

Any possibility of a bad injector(s), even though it passes the buzz test? I don't have a 7.3L injector tester at my dealer.

Yes, the buzz test only checks the top of the injector, and the majority of injector problems are in the bottom of the injector. On a very small percentage of trucks, you can have a leak of HP oil inside the injector into the fuel side, causing excessive oil consumption and blue smoke. Take a look at Mass Fuel Desired in scan data at a hot idle. (MFDES) Perfect numbers are 8-10 MG, and I'll "allow" 6-12MG. If it's up at 14-16mg, it probably need injectors. MFDES is kind of like STFT to a gas guy. If it's running poorly, chase that first- you state it starts fine, but if it's blowing Contribution codes, it's running bad.