Hello all,

I am having trouble getting my 2000 7.3 (200k) to start on the colder mornings. It will crank over fast, but won't start without a lot of tries. Today it took 6 pre-heats and cranks, but on others (and colder days) it has started easier. It does seem to be getting worse though.

I have replaced the glow plug relay recently so it *shouldn't* be that unless the replacement is fried. Starts fine the rest of the day and drives fine, but not in the cooler am (it was about 34 this morning). I also tested the batteries yesterday and while they aren't new, they tested okay.

Also, I read (briefly) about the CPS, but forgot to watch the tach this morning, but did notice it is pushing smoke out when turning over.

I am going to plug it in tonight to see if that makes a difference, but any help would be appreciated.

Thanks,
Dan

 

I'd have to initially guess it's either the relay or the glow plugs themselves. Do you have a good multimeter that will read in tenths of ohms as well as DC voltage? If so, you can check everything fairly easily without pulling valve covers.

 

I have a decent one and would be willing to check when I get home. How do I check and what ranges are okay?

 

To test the relay, set the meter to the first volts DC range above 12. Put one lead on each of the 2 larger lugs on the glow plug relay. Turn the ignition to ON. The reading will be the voltage drop between the two terminals. The closer to zero, the better. Since the problem seems to be intermittent, you should probably try it for several key cycles. If the oil temp is over 131F, the glow plugs won't activate at all. The colder it is, the longer the relay will stay activated (as long as 2 minutes when cold soaked).

For the individual glow plugs, if you pull the wiring connector off the valve cover gasket, there are 7 pins (on the gasket side). The front-most and rear-most 2 pins are the glow plug pins. Test resistance from each pin to ground. A new glow plug will be in the 0.6 to 2.1 ohm range. As long as they're somewhere in that ballpark, they should be OK.

 

Forgot to mention that some auto-ranging meters have trouble reading tenths of ohms below 1.0 . .

 

Thank you. I will test the relay in the morning when everything is nice and cold (assuming my tester will register the readings), but probably won't test the glow plugs until I'm at work and have more time. I'm assuming these readings wouldn't be affected by engine oil temp.

 

No, the glow plugs may vary a little bit with the temperature, but you should still get a usable reading.

 

So I think I did this right. The MM was set to VDC 20 and I tested it 6 times. The first number may be wrong in the tenths/hundredths as I didn't write it down.

Results are:

12.05
.15
12.05
12.05
12.05
.20--->.17

I'm presuming that when the glow plug relay reads 12.05 that it is not working, correct? It is new, but it's from CarQuest as it was easier to buy it on the farm account than drive to the dealer. Did I waste money not buying a Motorcraft one?

Also worth noting, I tried starting it after the final test, it did start, albeit unhappily, but it started no less. IF the glow plugs are not working at all, would it have still started? Temp was around 30/32 this am.

Thanks again.

 

Here is a video of how to test your relay.

You can simply ohm your glow plugs through the pins on your valve cover gasket, or go all the way back you you main harness

 

The relay is toast. It's intermittently working, but the contactor plate is probably pitted, causing it to only close the circuit occasionally. That's when it's reading 12 volts. When it works, it's the low readings. The Western snow plow relays are a good substitute, and cost about half of what the parts stores call a glow plug relay.

EDIT: Just noticed you said the relay is new. Either it's defective, or just not very good . . .

 

I decided to tag onto this thread as I am having the same problem hopes thats okay.

I measured each glow plug at the connector and all eight measured .7 to .9 ohms, I then measured the voltage drop between the two large posts on the relay and was getting .476V, almost a 1/2 volt drop, I only did it once but will try several times tomorrow when I have some one to turn on/off the key. Is ~.5V drop too much?

 

I should have waited a few minutes before posting, I was able to cycle the ignition a few times and the relay is closing about 25% of the time, looks like a new relay will be ordered tomorrow. Thinking about doing the White-Rodgers (Stancor) 586-902 GPR Replacement Mod, thoughts?

 

I just replaced my GPR with OEM from Ford it was $91 w/ 2 yr unlimited mile warranty. I also wired in a small LED light in the cab. Positive lead goes the GP side of relay, negative to battery. The LED lights up when the relay turns on and shuts off when it does. You KNOW when your GPR is working and for how long.