1991 GMC R2500 Suburban 350 TBI dies after a few minutes.

[eodcoduto]

I found a 1991 R2500 SLE suburban at a local mechanic shop that has been sitting there for two years and went to check it out. They body is perfect, barn doors, the interior is a solid seven and I am considering buying it. The problem is it’s a 350 and it’s not run for a year, the shop it is at is run by idiots and they cannot figure out how to keep it running for more than a few minutes. They changed two fuel pumps, and did wires and plugs and it will run for a few minutes and then just slows down very quick and cuts off. I did listen to it run and it sounded solid with a little bit of an exhaust leak. It feels like to me it’s the ignition control module or something in the coil the way it shuts off all of a sudden but since it is computer controlled, and I haven’t dealt with many of those, any thoughts?

 

[swettysblazer]

Oil pressure sender maybe? Once it warms up not reading right?

 

[eodcoduto]

I hadn’t thought of that

 

[swettysblazer]

I hadn’t thought of that

I would check by running power to the jumper on the fuel pump relay first and seeing if it still shuts off after that.

 

[eodcoduto]

I’ll see if the owner can get it away from the repair shop to let me diagnose it.

 

[scouthead]

catalytic converters can clog up... i had one on my 5.7 camaro that was 99 percent blocked. for a few days, i would drive it, and as the engine started heating up it would start loosing power... then the next day it stalled a few times.
after that it just didnt want to move under its own power, and then finally would only run for a minute before choking off and stalling.

if i had known at the time, i would have drilled a couple of 1/2 holes in the exhaust pipe somewhere in front of the cat. a section of pipe off the shelf at the auto parts store, cut in half, with 2 hose clamps would have probably made an acceptable patch for a while after diagnosing

 

[Blue85]

If it was a plugged cat, the lack of power would be very noticeable when trying to drive it. The easy test is to remove the O2 sensor so the exhaust has somewhere to go (easy if it's not seized in place, of course). A plugged cat would have lots of air shooting out of the hole. The official test is probably screwing a pressure gauge in there. You can also test with a vacuum gauge on the intake manifold. Without touching the throttle, the vacuum keeps decreasing until the engine stalls, due to the increasing backpressure.

For a fuel issue, installing a pressure gauge really helps, even though it's kind of hard on TBI. Then you can go after fuel filter, pump, relay, switch from there.

 

[Blue85]

Chances are this isn't a tough problem to solve. Maybe better to buy it while it's broken to get the best deal?

 

[eodcoduto]

I agree on getting it cheap, he wants $5000 if he can get it on the road and its worth that. I don't have time for a project so I'd have to low ball the snot out of him as is. I found a 1991 V2500 thats in daily driver shape that I am going to check out too.

 

[Blue85]

Man, if only you had some kind of online repository of square body knowledge.

 

[eodcoduto]

Man, if only you had some kind of online repository of square body knowledge.

I know, someone should come up with that for us.