When not plugged in my truck has trouble starting at temps below 50 degrees. It was 38 this morning, and with the truck not plugged in I had to crank for about 10 seconds before it popped off. I don't know if this is normal or not, but it seems excessive. I found that if I cycle the plugs twice it usually starts easier.

When plugged in for a couple hours the truck fires up immediately with only one plug cycle, even when it was about 20 degrees the other day. I have new motorcraft plugs that all passed with a test light. The WTS light stays for about 12 to 15 seconds depending on the temp. The truck has a new starter, and cranks at about 400 RPM.

I am worried I won't be able to start the truck after sitting at work all day in subzero temps this winter.
Any ideas what I should look at next? Maybe check to see if I have voltage at the harness to each plug?

Thanks.

 

How old are your injectors and injection pump mileage wise? An old fuel injection system can have retarded timing which can lead to tough cold starts. Does your motor smoke excessively and shake when it is cold? That's usually a good sign your timing is out of adjustment. It could also be air intrusion but cycling the glow plugs twice doesn't usually help that.

 

I'm told the truck has 225k miles. I do not know if the pump and injectors are original. The truck runs and idles very smooth once started though. It has good power, and only smokes grey for about 10 seconds at cold start up. Nothing I would call excessive though. Other than that it doesn't smoke at all unless I really get on it going up hill.

I thought maybe it was air intrusion, but I just replaced all of the caps and lines, and don't seem to have any drain back. I figured since it starts so well when plugged in it must be glow plug related.

I checked continuity in the wiring harness and it seems ok. I also checked and cleaned the ground for the controller. I wonder if maybe I should try bypassing the controller with a push button and see if that solves the problem?

Thanks for your help.

 

How does it sound after if fires up cold? Is it pretty smooth and mellow sounding? Or does it have a fair amount of clack and rattle?

 

Without being plugged in it has some rattle and clack to it. But it clears up pretty quickly.

 

I went out this morning after the truck had sat overnight and tested the glow plugs again. They passed the light test, and with a meter.

I then tested the glow plug relay. With the key off I have 12.4 V at the large terminal on the GPR that goes to the relay on the passenger fender, and 0 V at the other large terminal on the GPR. With the key on and the glow plugs cycling I have 12.4 V at the large terminal that goes to the relay on the passenger fender, and only 10 V at the other large terminal on the GPR. Am I correct in thinking this means I have a bad relay? Shouldn't I have more like 12.4 V on both terminals of the GPR with the key on and glow plug light on?

If this is the case any idea where the best place is to get a new relay?

Thanks.

 

That voltage sounds about right to me.
The plugs are taking a drain, thats why you only get 10 volts.

 

but it seems to me that voltage drop shouldn't be in the relay itself. it should be either in the battery or in the wires. if the relay itself costs him 2+ volts, that would indicate burned or corroded contacts in the relay, or corrosion on the outside of the relay where the wires connect

 

I tested it again and I must have done something wrong the first time. I am getting 10.5 V at both big terminals with the plugs cycling. So I think the relay is good.

 

Tom (AKA TJC transport) posted a video that showed cranking speed with bad batteries or cables compared to new. The first video sounded ok until you heard the second one. I couldn't find the post to give a link, but maybe your engine isn't cranking fast enough.

 

Like bashby said above, if the starter is getting tired, it will take longer to get it started. This was the case with my 90, I thaught the starter sounded good, untill I installed a new one. The difference is like night and day.

 

It has been in the low 20's in the morning when I leave. When mine is not plugged in it is a little harder to start. It got better after I read through the manual and followed the starting procedure they listed. Turn the key on and depress the throttle to allow the cold advance/highidle to set. When the light goes out hold the throttle from half to 3/4 (depending on temp) and crank the engine. This worked alot better for me than before when I would start it with no throttle. My starter is a little older though, so depending on the temp I will cycle the GP twice.

From my research there are a limited number of things that can cause it to be harder to start.
1. GP not functioning
2. Highidle/cold advance not working correctly
3. Starter not turning over fast enough
4. IP/Injector timing is not right
5. Compression issue

IT looks like your GP are working. You said you have a new starter, but could check your cables and batteries. For the high idle/cold advance you can turn the key to on, step on the throttle and then look at the plunger that extends to hold the throttle. then move onto having the timing checked. Compression would be an internal engin issue.

 

I checked over my battery cables and found that my positive cable is worn through the insulation in several spots, showing green corroded wires. Also the clamp on the battery post is so worn out it can be removed by hand even when tightened down all the way.

It seems strange that this would be the problem though, as the truck still cranks over at 400-500 rpm. I'm going to buy a new positive cable and see if that makes any difference.

Thanks everyone, I will let you know how it goes.

 

Yes, bad relay, in all likelihood. You'd expect the voltage to go down on _both_ big terminals with the key on and GPR energized, because the plugs are putting a load on the batteries. But the drop _between_ the terminals should be no more than about 0.3V. IOW, if you have 12.4V with the key off, you should expect, with the key on, something like 11.5 on the "always hot" side and about 11.2 on the other side. But since your voltage is dropping so much between the terminals, it's probably not energizing the plugs at all, so that's why the "always hot" terminal voltage isn't going down (IOW, the relay isn't allowing the GPs to actually draw significant current).

Easy enough to confirm - put a jumper cable between the two big terminals, see what the voltage does then, and also see what impact that has on how easily it starts. If indeed it starts better, that pretty-much means the relay is shot.

 

Nope, once the plugs are taking juice, the voltage drop will be 10 volt's and under....More like 9.7, or in that area.
These plugs take allot of juice, I personally don't think your relay is at fault.