Cold skip help - Diesel Truck Forum - TheDieselGarage.com
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post #1 of 4 (permalink) Old 10-20-2007, 04:25 PM Thread Starter
 
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Cold skip help

My 2000 7.3 skips in the morning when the outside temp is below about 60. If it happens to be closer to freezing it won't start at all. As soon as you hit the road and mash the accelerator beyond the half way point the skip imediately goes away. It was put on "the computer" and an injector test shows no problem. If you plug in the block heater all is fine. Doesn't really seem to be a glow plug problem. But, then again, I am still trying to figure out why a direct injected motor needs glow plugs in the first place!! My buddy is having the exact same problem with his truck. Anyone experienced this?
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post #2 of 4 (permalink) Old 10-20-2007, 05:38 PM
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Sounds like you have a glow plug or two out. Just because it is direct injected doesn't mean the fuel will burn when it's cold out.

'96 F-250 Extended Cab, GT'S injectors, GT'S intercooler install kit, custom turbo kit with a little HX40, Swamp's BIGEST oil.
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post #3 of 4 (permalink) Old 10-20-2007, 07:25 PM
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Direct injection has nothing to do with glow plugs or not, that is a compression ratio and cranking RPM feature.

The PSDs have glow plugs so they will start well in the cold weather. You could not sell a diesel P/U if it would not start much like a gas. Basically P/U owners are unwilling to tolerate the things that truckers deal with to start their rigs at -10*F.

There are a number of possible causes for your problem, GPs are certainly one, but with the PSD engines, GP failures are truely very rare. If the GPs are not working correctly, it can commonly be traced to a bad GPR or damaged terminals at the UVC harness connector(s) (Under Vavle Cover).

The fuel injector coil gap bay now be wide enough so the magnetic force from the coil is simply no longer strong enough to lift the armature off it's seat when the oil is COLD, but once it begins to work it functions normally.

The first thing to check are the GPs and the GPR to ensure they are working properly. The GPs should light a test light connected to BATTERY power brightly. You can carefully probe the outermost two terminals on each of the four UVC connectors to test them. Any one that does not light brightly is suspect. Testing the GPR involves measuring the voltage on BOTH LARGE terminals while the WTS light is on. The voltage MUST be the same within 0.5V or the GPR is bad. Aftermarket ones fail sooner and have higher voltage drops when new then OE parts.

Oil viscosity can make the injectors "lazy", one test of the injectors is to simply change the oil to a known name brand of 10W-30 (cold months) that is API rated "CI-4" for Diesels, then to retest the cold start performance. If a simple oil change fixes the misfire or romp, then you can *suspect* that injector coil shimming may well fix your problem (if everything else checked out OK).

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post #4 of 4 (permalink) Old 10-21-2007, 06:24 AM
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It seems the last time I saw someone have issues with the armature clearance being to tight they had issues running when hot not cold but it's been awhile so I could be off. However I do highly recomend NOT shimming the armatures if they are worn. That is an excellent way to cause other problems like the armature hitting the solenoid. The only way to properly fix it is with some machine work and tearing the injectors completely down.

From my experience the injectors usually seem to work better when cold than when hot if there are any oil related issues with them which leads me more to thinking a glow plug is the culprit here. I would check out the glow plugs first as it's the easiest thing to do.

'96 F-250 Extended Cab, GT'S injectors, GT'S intercooler install kit, custom turbo kit with a little HX40, Swamp's BIGEST oil.
466 on #2 only
739 with NČO

13.544 in 1/4 mi!

"If you think you can do a thing or think you can't do a thing, you're right." Henry Ford

Yeah I can keep up!:Thumbup:
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