creich68
Member
- Joined
- Jul 2, 2023
- Posts
- 35
- Reaction score
- 66
- Location
- North Carolina
- First Name
- Clay
- Truck Year
- 1991
- Truck Model
- V1500 Burban
- Engine Size
- 5.7
Hello all!
I'm perplexed...I think the repair shop is getting there too.
I recently had my suburban break down on the weekend shortly after leaving the house. The engine bucked a couple times before briefly stumbling and dying. Coasted into a parking lot and had it towed to a local shop. It would crank but not even try to fire up, no matter what. Dropped it off at the shop and while waiting my a ride, I tried cranking it again. It did start up after a quite a bit of cranking, but was still running a little rough.
Upon speaking with the shop the next day, their initial diagnosis was that there was a vacuum leak with the throttle body gasket, one of the rubber hoses plugged into the throttle body was dry rotten (vacuum leak #2) and that the intake manifold gaskets were also leaking (vacuum leak #3). Plausible as I know vacuum leaks can cause issues. Didn't quite explain the abrupt change/dying, but at 180k miles, it's not helping the cause. I gave the green light on the work and a few days later picked it up....a brief rewind - while my parents had the suburban stored in a barn, a mouse had chewed on the wiring harness on the intake manifold. My dad spliced the wires back together and hasn't had an issue until now....I asked the shop to check the connections while they were performing the gasket work just to make sure that wasn't a contributing cause. They did and found one butt connector loose, and fixed that. The distributor was also a little rusty inside and the tech said the shaft was catching a little bit when spinning from the bottom. They recommended a replacement OE distributor, and for the few extra bucks, I gave the green light on that. I'd hate to put it all back together and that be an issue not far down the road.
I picked the suburban up yesterday and on the way home the engine stumbled briefly and then started running as normal. Only the one time and never died completely. Made it back to the house and shut it off. A few mins later I tried starting it and it just cranked. No start unless I floored the gas pedal. I finally got it started and since it seemed to be running okay, I drove it back to the shop so they could take a second look the next morning. Once I got to the shop, shut it off, and tried restarting. This time it would crank, but would start as soon as I let off the key (return to the on position by the internal spring). This happened every time I shut off and restart....crank and crank, but as soon as I let off the key, fired up. What's odd is when I picked it up from the shop that afternoon, it fired up immediately without having the let off the key to force it.
Today I went by the shop first thing in the morning to explain the key situation and intermittent stumbling. Showed them a video of it when occurring for reference too. Shop looked over the wire harness again and found a second butt connector loose on the wire to the Coolant Temp Sensor. They checked the whole harness and fixed the loose connection. Both the tech and shop owner drove it without issue. I picked it up this evening and drove it home. Ran great the entire way home. I think the loose connectors fixed the intermittent running issue. Shut if off in the driveway and went to restart it a couple mins later. Same issue - cranks, but only fires after letting off the key. Every time...whether I crank it a short amount of time, or extended time.
So I'm perplexed - what would cause it to crank but only fire after letting off the key??
- Is the coil on the new distributor not sending juice to the ignition while cranking, but it does when in the On position? And because the engine is still spinning from cranking it starts?
- Is it the ignition switch itself? Seems odd considering it was not doing this prior to breaking down initially
- Is it fuel pump or fuel pump regulator related? The fuel tank/pump/filter was replaced about 5 years ago (10k miles) but I wouldn't be shocked if an aftermarket pump doesn't last as long as the original.
- Is there a fuel pump relay on these TBI engines?
Anything I'm not considering but should check, or suggest to the shop? They have been good this whole time, and I'm being friendly because I know these little gremlins can be difficult diagnosis. Just puzzling why it's behaving this way.
I've googled this with a variety of results from forums other than here. Any thoughts and ideas are welcomed and appreciated!!
Update - I let it cool down for about an hour. It did start while cranking without letting off the key, but it took a little bit of cranking. Took it around the neighborhood and let it come back up to temp. Same issue, cranks but fires after letting off the key. The last attempt it tried to fire but wouldn’t start but ran as soon as I let off the key. So strange. Seems to run well, but slight hunt’s rpm at idle. So Slight enough I’m not sure if it’s really an issue. For reference the IAC was replaced about 1.5 yrs ago.
I'm perplexed...I think the repair shop is getting there too.
I recently had my suburban break down on the weekend shortly after leaving the house. The engine bucked a couple times before briefly stumbling and dying. Coasted into a parking lot and had it towed to a local shop. It would crank but not even try to fire up, no matter what. Dropped it off at the shop and while waiting my a ride, I tried cranking it again. It did start up after a quite a bit of cranking, but was still running a little rough.
Upon speaking with the shop the next day, their initial diagnosis was that there was a vacuum leak with the throttle body gasket, one of the rubber hoses plugged into the throttle body was dry rotten (vacuum leak #2) and that the intake manifold gaskets were also leaking (vacuum leak #3). Plausible as I know vacuum leaks can cause issues. Didn't quite explain the abrupt change/dying, but at 180k miles, it's not helping the cause. I gave the green light on the work and a few days later picked it up....a brief rewind - while my parents had the suburban stored in a barn, a mouse had chewed on the wiring harness on the intake manifold. My dad spliced the wires back together and hasn't had an issue until now....I asked the shop to check the connections while they were performing the gasket work just to make sure that wasn't a contributing cause. They did and found one butt connector loose, and fixed that. The distributor was also a little rusty inside and the tech said the shaft was catching a little bit when spinning from the bottom. They recommended a replacement OE distributor, and for the few extra bucks, I gave the green light on that. I'd hate to put it all back together and that be an issue not far down the road.
I picked the suburban up yesterday and on the way home the engine stumbled briefly and then started running as normal. Only the one time and never died completely. Made it back to the house and shut it off. A few mins later I tried starting it and it just cranked. No start unless I floored the gas pedal. I finally got it started and since it seemed to be running okay, I drove it back to the shop so they could take a second look the next morning. Once I got to the shop, shut it off, and tried restarting. This time it would crank, but would start as soon as I let off the key (return to the on position by the internal spring). This happened every time I shut off and restart....crank and crank, but as soon as I let off the key, fired up. What's odd is when I picked it up from the shop that afternoon, it fired up immediately without having the let off the key to force it.
Today I went by the shop first thing in the morning to explain the key situation and intermittent stumbling. Showed them a video of it when occurring for reference too. Shop looked over the wire harness again and found a second butt connector loose on the wire to the Coolant Temp Sensor. They checked the whole harness and fixed the loose connection. Both the tech and shop owner drove it without issue. I picked it up this evening and drove it home. Ran great the entire way home. I think the loose connectors fixed the intermittent running issue. Shut if off in the driveway and went to restart it a couple mins later. Same issue - cranks, but only fires after letting off the key. Every time...whether I crank it a short amount of time, or extended time.
So I'm perplexed - what would cause it to crank but only fire after letting off the key??
- Is the coil on the new distributor not sending juice to the ignition while cranking, but it does when in the On position? And because the engine is still spinning from cranking it starts?
- Is it the ignition switch itself? Seems odd considering it was not doing this prior to breaking down initially
- Is it fuel pump or fuel pump regulator related? The fuel tank/pump/filter was replaced about 5 years ago (10k miles) but I wouldn't be shocked if an aftermarket pump doesn't last as long as the original.
- Is there a fuel pump relay on these TBI engines?
Anything I'm not considering but should check, or suggest to the shop? They have been good this whole time, and I'm being friendly because I know these little gremlins can be difficult diagnosis. Just puzzling why it's behaving this way.
I've googled this with a variety of results from forums other than here. Any thoughts and ideas are welcomed and appreciated!!
Update - I let it cool down for about an hour. It did start while cranking without letting off the key, but it took a little bit of cranking. Took it around the neighborhood and let it come back up to temp. Same issue, cranks but fires after letting off the key. The last attempt it tried to fire but wouldn’t start but ran as soon as I let off the key. So strange. Seems to run well, but slight hunt’s rpm at idle. So Slight enough I’m not sure if it’s really an issue. For reference the IAC was replaced about 1.5 yrs ago.
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