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Old 11-26-2008, 10:04 AM
jor jor is offline
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Won't Run

87 Suburban 5.7L TBI

It's not a hot rod but I've gotten great advice here in the past and I'll give it another try.

I was out doing some 4-wheeling the other day and really enjoying this old Suburban. It was running and performing great. Anyhow, on the way out of the area I stopped to get back into 2WD. As I reached down to move the selection lever the engine kind of chugged and quit. From then on, it would turn over, try to start but would not keep running. I'm looking for some ideas on how to proceed.

I believe it is a fuel delivery issue. Yesterday, I disconnected the fuel line and turned the engine over - lots of fuel into my glass container. I removed the filter and determined that it does not restrict flow. Finally, I poured a little gas directly into the carb - it started right up and ran for a few seconds until the fuel was gone.

Thanks.
jor

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Old 11-26-2008, 11:08 AM
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Quote:
Originally Posted by jor
87 Suburban 5.7L TBI

It's not a hot rod but I've gotten great advice here in the past and I'll give it another try.

I was out doing some 4-wheeling the other day and really enjoying this old Suburban. It was running and performing great. Anyhow, on the way out of the area I stopped to get back into 2WD. As I reached down to move the selection lever the engine kind of chugged and quit. From then on, it would turn over, try to start but would not keep running. I'm looking for some ideas on how to proceed.

I believe it is a fuel delivery issue. Yesterday, I disconnected the fuel line and turned the engine over - lots of fuel into my glass container. I removed the filter and determined that it does not restrict flow. Finally, I poured a little gas directly into the carb - it started right up and ran for a few seconds until the fuel was gone.

Thanks.
jor
Between TBI and carb, which is it?

Bogie
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Old 11-26-2008, 11:41 AM
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87 would be TBI. If it is stock.
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Old 11-26-2008, 11:45 AM
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Check your fuel pressure it should be 9-13 psi on a 350 with TBI....
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Old 11-26-2008, 02:43 PM
jor jor is offline
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Thanks for the answers. My &^%^& internet access has been down so I'm just getting back. Like mtz said, it is TBI. Here's what I've done:

* Checked fuel pump operation (2 seconds when key on);
* Checked fuel filter
* Checked TBI injectors (no gas when disconnected, both spraying when connected.
* Checked TBI injecters (both are pulsing)
* Opened the distributor bypass (same problem).

It starts and then immediately dies. If I pour gas down the throats, it will run. I'll check the pressure. Any other ideas out there? Thanks.
jor
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Old 11-26-2008, 02:55 PM
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this might be out there in left feild, but have you checked the oil for a gassy smell, u might have a bad head gasket. had this happen to an old ford taruas i had, it would run for like 2or 3 days, then the dam thing wouldn't start till i changed the oil
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Old 11-26-2008, 03:18 PM
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Again, whats the fuel pressure? it can be pumping fuel in but if it`s not enough to run it`s not going to, you must know the fuel pressure otherwise your chasing your tail. Not long ago I went by a sporting goods store in my fathers 98 sierra pickup, I shut it off and went in, got what I was after got back in the truck and hit the key, it started and idled really rough, I gave it some pedal wondering what was going on, it stalled and went dead.
I guessed the fuel pump went out. I got the truck towed home and checked the fuel pressure, it had 30 psi and it requires over 50psi to run, it had just enough pressure to idle. On the TBI as said it should be 9 to 13 psi. If it`s less than this it won`t run. If the fuel pressure checks out okay then it sounds as if you have a rather large vacuum leak.
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Old 11-26-2008, 03:28 PM
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1986 Was the 1st year of 1st generation of Vortec {technically speaking}

it has ECM TBI & electric fuel pump

If the Fuel pump is not pumping enuf It will trip the oil switch which will kill the ignition.

Check fuel pressure. filter & then the TBI injectors.

If it will start & run using a gas bottle then I would bet the farm its the fuel pump.


When using a gas bottle try to use something like a qt 90wt bottle be careful of jumping sparks & gas in your hand!



R
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Old 11-26-2008, 04:28 PM
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Have the main, and fuel pump relays tested, or replace.

Check your battery cables, to see if either the positive, or negative loosened up under the vibrations.

Grab ahold of the main wire loom that the distributor wires come out of. See if it pulls on the distributor plug in's, if so yank on it to give a little more slack, and push in on the individual wires at the distributor connections.

Check the EGR valve for a chunk of carbon holding it open.

Check the idle air control for proper operation.

Check the neutral safety switch, and vehicle speed sensor, for loose connections.

Have the ignition module tested.
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Old 11-26-2008, 05:48 PM
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I had the same problem one time. Replaced the distributor with a spare I had and it fixed the problem. Not sure which componet in the distributor was the culprit. Probably the module not pulsating the injectors.
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Old 11-27-2008, 07:28 AM
jor jor is offline
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Thanks to all for your input. I'm having connectivity issues too (when it rains...) and haven't been able to post. Comcast is coming out today to fix it (must be the low man on the totem pole to work on Thanksgiving!). Not sure if this will post but...

Smrat: No gas in the oil (thankfully).

Dblvision: Fuel pressure. See below.

Rob Keller: Gas bottle? I usually just pour a little gas down the throat and give it a try. I'm guessing the gas bottle might make this activity safe?

Carsavy: EGR? I meant to check that and will. I didn't think it would actually prevent a motor from running though. The IAC is good. I can't find the damn fuel pump relay!

Well, I rugged up a pressure gauge. Not sure I did it right but I installed it on the outlet side of the fuel filter. (just disconnected the fuel line and terminated the line at the gauge). When I turn on the ignition, it reads only 1 psi and when cranking it doesn't even hit 3! If I have this rigged right, I guess this points to the pump or regulator.
jor
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Old 11-27-2008, 10:39 AM
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Quote:
Originally Posted by jor
Thanks to all for your input. I'm having connectivity issues too (when it rains...) and haven't been able to post. Comcast is coming out today to fix it (must be the low man on the totem pole to work on Thanksgiving!). Not sure if this will post but...

Smrat: No gas in the oil (thankfully).

Dblvision: Fuel pressure. See below.

Rob Keller: Gas bottle? I usually just pour a little gas down the throat and give it a try. I'm guessing the gas bottle might make this activity safe?

Carsavy: EGR? I meant to check that and will. I didn't think it would actually prevent a motor from running though. The IAC is good. I can't find the damn fuel pump relay!

Well, I rugged up a pressure gauge. Not sure I did it right but I installed it on the outlet side of the fuel filter. (just disconnected the fuel line and terminated the line at the gauge). When I turn on the ignition, it reads only 1 psi and when cranking it doesn't even hit 3! If I have this rigged right, I guess this points to the pump or regulator.
jor
Rigging up a pressure gauge, this way, is what we call 'dead head' pressure. This checks the maximum fuel pump pressure output. Your fuel pump, or a connection hose in the tank, is bad.
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Old 11-27-2008, 12:32 PM
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3psi isn't going to be enough... The pressure between the fuel pump and all the way to the regulator in the TBI will be the same pressure.
So you've got 3psi at the head of the injectors when you need 9-13psi.

The TBI pumps are half the cost of high pressure pump.

Replace that and the filter while your there.

You'll be up and runn'n again.
~Scott
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Old 11-27-2008, 06:06 PM
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Yep,fuel pressure is the first thing to check and from what I have read...you don't have enough.

Like the others have mentioned...you need at least 10spi to run properly and 12-13 being ideal.
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Old 11-27-2008, 08:02 PM
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it sounds like it.s the pump. if its going bad, but still works it just wont put out the right pressor for the injectors. maybe it looks good coming out into a jar but it should really push it out
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