Hard start. Where to look besides GPs and GPR - Ford Powerstroke Diesel Forum
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Old 04-24-2013, 01:13 PM
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Hard start. Where to look besides GPs and GPR

Since mid winter this year I have been having a similar problem. I'm in Utah and plug the truck in when it's really cold (below freezing). But since spring I haven't been plugging it in and if the truck has sat for a while it has a hard time starting.

This is what it does. I'll cycle the glow plugs once or twice and it won't start. I cycle them again and it will sputter a little and puff white smoke. On the 4th cycling of the glow plugs it will star but will run rough, hard lope. It will also puff a little white smoke. This clears up after about 30 seconds.

This is what I have checked so far. Tested the glow plug relay. This included supply voltage on the small terminals with the key in the on position. I also ohmed across the large terminals and when voltage is supplied to the small terminals and got no resistance well .01 I can also hear the autable "click" when voltage is applied. So I'm fairly confident the relay is good.

The next thing I tested was the glow plugs themselves. I did this by removing the plug to the valve cover gasket and ohming the outside 4 prongs. All 8 show no resistance. As a side note the glow plugs are Motorcraft and were replaced two years ago along with the GPR.

I don't think the problem is the oil weight because I have been running 15w40 in the truck since I bought it and when the GPs and GPR were new it would start fine below at or just above freezing without plugging it in an having not been run for weeks.

As far as the starter and batteries go the batteries are about 18 months old and the starter cranks good and hard. It doesn't seem to be slow or have a hard time cranking. Also I did an injector buzz test on it about a month ago, well after the had start problem started, and all eight buzzed just fine. On the cylinder contribution test It has always failed in the #8 that could be a factor but it was failing in that cylinder long before the cold start problem.

Any help on this problem would be greatly appreciated.
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Old 04-24-2013, 01:57 PM
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First, you should always post the yr of your truck for best results

Next, stop "cycling" the GPs. The WTS light has Nothing to do with IF or How Long they're ON (they're on when the light is out, and even Not On when it is sometimes...) So, turn the key, leave it on for between 1-2mins depending on how cold it is (even though the WTS went off long before that) and try to start.

Also, what do you mean "All 8 show no resistance"?? That would me that're all BAD (unlikely, recheck following this link -> Troubleshooting GPR & GP's)

What temps are you dealing with now? Does it do this even if it's 40F out?
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Old 04-25-2013, 03:23 AM
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Thanks NoRalPh for your quick response. Sorry about not posting the year but it's a 99.5. The temperature today was about 65 F and itís had a hard time starting at temps above 70

Thanks for the link to the GPR & GPs Troubleshooting. I hooked up my autoenginuity scan tool and confirmed how long the GP's are actually on after the WTS light comes on and you were dead on about the GPs staying on well after the WTS light goes off.

As far as the resistance or ohms on the GPs the multi-meter I'm using has a feature that gives an audible tone when there is little to no resistance and there is no tone when there is resistance. It will also display the ohms. When I first did the test I only listened for the tone to tell me that I did not have infinite resistance. I did the test again looking at the display and found all to be within the .6 to 2 range.

I still had the old GPR that I took out of it two years ago. It was still working when I replaced it so I held on to it. (I replaced it with the GPs because I was making a trip to North Dakota in January and wanted the peace of mind.) I threw it in there and tested it (using the steps in the link you posted) and it tested fine. However since the truck was already warm Iíll have to wait till tomorrow to find out if thatís the problem. Thanks again for your help.
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Old 05-05-2013, 12:16 PM
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Update. I found the problem for my hard starts and it ended up being the GPR. Who would have thought I could have and 0 ohms across the large terminals when the GPR was energized and still have 0 volts on the GP side of the relay. I guess the little electric gremlins were at it again. I took the old relay apart and this is what I found. You can see where it had been arcing.

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Old 06-01-2013, 03:09 AM
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It is very easy to have continuity to read 0 ohms and not be able to carry current to power the GPs.

The best way to have figured that out (and how I did it) was to put a voltmeter on the outgoing post during the warming cycle to check voltage. You would not have seen a voltage, thus realizing that the GPR could not handle the load the GPs wanted to absorb.

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