Injector Pump Heat Soak or GP Controller?

scjarena

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1990 7.3 starts normal when cold. Lately its been hard when hot, like when its been parked for about 20 mins when hot. I've read online about this being a sign of worn IP and some suggested pouring a little cool water on head of IP. A diesel mechanic friend said I also need to check the GP controller. Has anyone heard of the GP controller causing hot hard to start issues?
 

gandalf

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Start with the most simple. When the engine is hot and refuses to start pour some cool water, NOT cold, over the IP. If this cures the problem, realize it's only temporary. Your IP is indeed suffering from heat soak, and should be replaced.

We, the forum members, strongly suggest and recommend only 4 IP rebuilders. They are all members here. I'll let some one else list them. We all have our favorites.
 

scjarena

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I can tell you, you do not need glowplugs when the engine is warm, even though the controller may turn them on for a little bit
Thats what I would think. It should fire right off when hot. I'll try the cool water on the IP and see what happens.
 

Big Bart

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Where to buy

 

scjarena

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After a 15 mile round trip, 95degs out, parked for a couple min., started right up. Parked for 15min, cranked on it and wouldn't start. I poured a couple cups of about 80 deg water on IP, didn't start extremely quick, but did start. I guess I'll be looking for an IP.

One thing, though, I don't care about the WTS light, but just curious, when it is hot the WTS doesn't come on with the key on, is this normal? When cold, light comes right on.
 

franklin2

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After a 15 mile round trip, 95degs out, parked for a couple min., started right up. Parked for 15min, cranked on it and wouldn't start. I poured a couple cups of about 80 deg water on IP, didn't start extremely quick, but did start. I guess I'll be looking for an IP.

One thing, though, I don't care about the WTS light, but just curious, when it is hot the WTS doesn't come on with the key on, is this normal? When cold, light comes right on.
The automated glowplug system on these trucks is very touchy when it comes to wiring harness condition/resistance. These trucks are getting old and so is the wiring. As time goes on, you will either spend a lot of time and money keeping the automated glowplug system working, or just go to a manual switch.
 

Cubey

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One thing, though, I don't care about the WTS light, but just curious, when it is hot the WTS doesn't come on with the key on, is this normal? When cold, light comes right on.

Yes, normal. Both my 85 6.9 with the 6.9 style controller, and my 87 6.9 with the 7.3 style controller do that. Both fire up perfectly when WTS doesn't come on for a warmed up engine. The controller senses it's hot enough already and doesn't need the glow plugs, so it never fires them up.
 

rhkcommander

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How's the exhaust look? Exhaust tells a lot of stories. Exhaust at cold idle, warm idle, WOT, etc.

It's not the glow plugs, that much is certain.

It's probably the IP, but you could have other contributing factors too: weak compression, air intrusion, weak starter. Batteries/stock alt getting tired if you're only doing a 15 minute trip, it's probably not enough time to recover the power from GP and starter.

Blue exhaust means you're burning oil, compression is low. Gray at cold start is normal. Black when working hard is normal. Anything else could be abnormal.

My old engine was critically low on compression. The prior owner sucked a bunch of sand right before selling it to me, so the compression went south fast. I had to glow EVERY time I went to start it, unless it was under probably 10-15 minutes. It started fine in the summer but boy it hated winter, I needed the batteries in tip top shape, good new starter, and fresh plugs (bosch, which I felt ran hotter) on a manual button. Then it did OK, but if any of those qualifiers slipped up, like the batteries not being topped up, or 2+ dead plugs and she was not moving without a pull-start. Ran great when it was started, being turbo and all. Just a lot of blue, oh and it ran away once but being a manual you just upshift hard to ***** it. If it's an auto and she runs away, good luck. Assuming non-turbo Jam towels down the intake if you can get to it before it blows, if turbo get a thick piece of wood over the intake, just not your flesh, it's basically a garbage disposal from hell.


In fact I know the bosch glowplugs run hotter, I could manually hit them for 7 seconds and start up, with the Motorcraft it took much longer. But you can't deviate if you use the glow plug controller , it'll murder any hot plug - only Motorcraft beru or 12V-proper plugs can take that caveman technology abuse.
 

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