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I know-OH GREAT-he has ANOTHER problem child to heal!

This one is a 1990 GMC K2500 Extra Cab 4X4;5.7L,700-R4  

The  PO says it quit him on the highway,he put a new fuel pump in it and it still wouldn't start. Here's what I've tried so far. I listened for the pump running,it did, dumped 5 gallons of fresh gas in the tank (The gauge showed empty),tried bleeding the lines to the T/B,the left pipe showed fuel,the right side pipe,not so much,(It was EXTREMELY tight,and the nut was rounded,it took a pipe wrench to finally get it loose),and that's about all I had time for. I suspect maybe

A-an ignition module

B-an ECM

C-a plugged fuel filter

Next will be checking the codes,which I SHOULD have started with,but I really expected it to be an easy fix.

   Other issues with this truck are 2 light bulbs out,the right fender scuffs the door,the left window (power) is missing a piece of the channel and the switch doesn't work,and the shift indicator doesn't work. I'd be surprised if the A/C works.

    Speed

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You do know how to find them, Speed!  This should be a solid truck, basic to work on considering the modern trucks...I'd try the fuel filter first and foremost.  This is the most common "suddenly stopped running" fix for EFI systems.  TBI is reliable and basic.  We can delve deeper if the filter does not do it.  Codes are always helpful, even on earlier OBD systems.

Moses

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The '90 GMC's a runner. I replaced the gas filter,which was plugged almost completely,but still no start. Next I pulled the ignition module and had it tested-it failed. I bought a new one and installed it and the engine started after about 3 seconds of cranking. Runs a little cobby,but I'm sure that's just stale gas. So far everything works except one back up light and one tail light bulb,soon to be replaced.

   Next,I'm working on getting the clutch hydraulics replaced on the '93 Ford Explorer I recently bought.

   Speed

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Your fleet is operational, Speed!  Yea...One GMC truck done, just the Explorer clutch hydraulics to go...Fast diagnostics and a ready fix on the '90 Jimmy!

Moses

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I'd been trying to get the previous owner to work with me in getting a Title on this truck,but it sounds like there's a second name on it that belongs to an ex-girlfriend/drinking buddy he REALLY doesn't wanna talk to,so it looked like an alternate method was the only option. I decided to cut my losses and sell it as is,as a parts truck,so I advertised it online. A local rancher bought it for $750.00;he has a Diesel powered one a couple of years newer with an exploded engine and wants to use this one for the Engine/Trans./T/C to swap in,as I understand it. I told him to get logged onto this Forum for advice and information. Don't know how soon he plans to start his project,but hopefully you'll be hearing from him by Spring.

   Speed

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He's not losing much by getting rid of the 6.2L/6.5L GM diesel.  The turbo 6.5L version was okay, naturally aspirated  they were not impressive.  We had a mid-'90s Suburban 2500 test vehicle with this engine;  the 6.5L had a stronger lower block assembly and turbocharging, it ran quite well, made enough noise and got marginal fuel economy.  The gas engine is probably a match for fuel efficiency.

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It sounds like his main concern is what he'll need to save out of the wiring to make the gas engine work in a Diesel truck. He also says the Diesel is a 5 speeder,but the gas engine is mated to a 700R4,so is there a way to keep the stick and link it to the 5.7L gas motor? If not,I guess he can use the auto. and whatever wiring goes to it,and change to the gas ECM. I don't think I'd get much enjoyment from doing this kinda conversion on something with all this electric junk to figure out and cross-match.

   Speed

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An Allison transmission?  The 4L80E four-speed (OD) was typically used in the '90s unless his truck is either heavy duty or has a transmission swap.  Wiring will be his bigger challenge, overlaying the chassis wiring schematics to compare the differences then splicing or swapping harnesses.

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I'm told the 700R4 was GM's first 4 speed OD  automatic,meant to replace the old T350,and eventually replaced the T400 too,then came the 4L60 and the Heavy Duty 4L80 series. Since it's a '90 Heavy Half,it was,I think,the first year of the 700R4 replacing the T400 in the  heavy duty half ton models. I agree,the mechanics of the conversion,while likely expensive ,won't be that hard,but the electrics will be a nightmare.

   Speed

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