TBI fuel injector trouble?

[jteck10]

Here i am resorting to the most helpful outlet for this truck that i know of
my '90 K5 blazer now will start, but stalled on me 4 times on the way home (a 3 mile ride from where i was)

backstory:
noticed my water pump was leaking a week or so ago. got a new one, replaced it along with a new water outlet housing and thermostat
drove it up and down and all around for 2 days, then it stalled on me 4 blocks from my house.
couldn't diagnose, so i had it towed to a local shop who said it was a busted ignition control module (i replaced cap, rotor, plugs, and wires at the beginning of the year)
they replaced it, and it ran fine.
today, 3 days later - it died on me 4 times on the way home (a 3 mile drive)
each time i would pull over, let it sit for 30-45 seconds and start it up again.
it would take a second or two of cranking more than normal, but would start up.

drove it home and cant figure out what's wrong.
used an ODB1 code reader and no codes came up.
left it on in the driveway for about 20 minutes and its fine. stepped on the gas an all.

my fuel injectors seem way louder than usual - could they be failing?
the fuel injectors were new towards the beginning of the year as well

video for reference on how loud they are

appreciate the help in advance!

 

[dyeager535]

Few things:

Does the check engine light work properly?

Do you have to wait that long to get it to restart? If so, have you checked for spark as soon as it dies? Hard to do without a helper.

Do you hear the fuel pump prime when you turn the key to run (not start)? You can only test that once every ~15 seconds.

Have you checked fuel pressure?

Also, if you download your year service manual(s) in my signature, I'm betting there is a troubleshooting flow chart for engine stalls.

If you question the injectors, IIRC its a resistance test across the terminals, but best done hot, like right when it fails.

 

[jteck10]

Few things:

Does the check engine light work properly?

Do you have to wait that long to get it to restart? If so, have you checked for spark as soon as it dies? Hard to do without a helper.

Do you hear the fuel pump prime when you turn the key to run (not start)? You can only test that once every ~15 seconds.

Have you checked fuel pressure?

Also, if you download your year service manual(s) in my signature, I'm betting there is a troubleshooting flow chart for engine stalls.

If you question the injectors, IIRC its a resistance test across the terminals, but best done hot, like right when it fails.

Does the check engine light work properly?
- i think so? previous to the shop putting in the new ICM, it read a code 43. that code is now gone but my ABS light is blinking. i'll test that code in a bit

Do you have to wait that long to get it to restart? If so, have you checked for spark as soon as it dies? Hard to do without a helper.
- not really, usually about 30 sec does the trick. i havent checked for spark soon as it dies because it only happens while driving.

Do you hear the fuel pump prime when you turn the key to run (not start)? You can only test that once every ~15 seconds.
- i tried listening to it but without a helper i cant hear it on my own

Have you checked fuel pressure?
- not yet, thats on the list to do today

Also, if you download your year service manual(s) in my signature, I'm betting there is a troubleshooting flow chart for engine stalls.
- ill check it out, thanks!

If you question the injectors, IIRC its a resistance test across the terminals, but best done hot, like right when it fails.

 

[dyeager535]

Check engine light should come on, blink off then stay on when you turn the key from off to run. Should stay lit as long as you don't start it.

To my knowledge ABS should have nothing to do with the stalling, but I know very little about how it's powered and what not.

Do you have bad hearing? Not being a jerk, just that normally the pump can be heard pretty clearly as long as there isn't a ton of ambient noise. My hearings not that great and I can hear it ok. May help to stand outside the truck and turn the key while you are as close to the tank as possible.

I would test pressure at the fuel filter, and replace it while you are there if it hasn't been done recently. On principle I'd stay away from Fram. Wix is usually pretty good stuff, and relatively cheap.

 

[scouthead]

Here i am resorting to the most helpful outlet for this truck that i know of
my '90 K5 blazer now will start, but stalled on me 4 times on the way home (a 3 mile ride from where i was)

backstory:
noticed my water pump was leaking a week or so ago. got a new one, replaced it along with a new water outlet housing and thermostat
drove it up and down and all around for 2 days, then it stalled on me 4 blocks from my house.
couldn't diagnose, so i had it towed to a local shop who said it was a busted ignition control module (i replaced cap, rotor, plugs, and wires at the beginning of the year)
they replaced it, and it ran fine.
today, 3 days later - it died on me 4 times on the way home (a 3 mile drive)
each time i would pull over, let it sit for 30-45 seconds and start it up again.
it would take a second or two of cranking more than normal, but would start up.

drove it home and cant figure out what's wrong.
used an ODB1 code reader and no codes came up.
left it on in the driveway for about 20 minutes and its fine. stepped on the gas an all.

my fuel injectors seem way louder than usual - could they be failing?
the fuel injectors were new towards the beginning of the year as well

video for reference on how loud they are

appreciate the help in advance!

im interested to hear this when i can step away from the office

im thinking lack of fuel pressure? but i guess you would see the gas spraying out...

ive had a different truck giving me similar issues in the past- ended up being crap in the gas tank- would clog the sock on the fuel pump under load... and a few min later gravity would take over, and enough of the junk would fall off to allow it to start again... 20 dollar blue tooth amazon flexible snake camera is my go to for things line this now- can take a look around inside a cylinder, or gas tank, or whatever without taking things apart.


also, i had a 1995 Camaro that had your symptoms when the catalytic converter failed. the back pressure would load up and cause the engine to stall. soon after that started, it was a struggle to keep it running, and i had to feather the clutch and keep the rpms down... soon after that, it was just plain undriveable. If i had taken the time to drill a 1/2 inch hole in front of the cat, and weld a washer or scrap over it after the test, I probably would have put the new cat on it and kept that car (and probably be in jail from all the speeding tickets)

 

[scouthead]

Few things:

Does the check engine light work properly?

Do you have to wait that long to get it to restart? If so, have you checked for spark as soon as it dies? Hard to do without a helper.

Do you hear the fuel pump prime when you turn the key to run (not start)? You can only test that once every ~15 seconds.

Have you checked fuel pressure?

Also, if you download your year service manual(s) in my signature, I'm betting there is a troubleshooting flow chart for engine stalls.

If you question the injectors, IIRC its a resistance test across the terminals, but best done hot, like right when it fails.

im going to try and remember the bit about the hot test on injectors- that's interesting

 

[Wes Harden]

It sound electrical to me. 30 seconds restart is a little quick for an over heated pump to start working again.
The wires for the injectors at the tbi are suspect too. the insulation cracks and flakes away.
A visual inspection of the injector spray while running, should have a nice cone shaped pattern, with no gaps.
While engine running wiggle the plugs at the distributor, and the fuel pump relay on the firewall.

 

[jteck10]

Check engine light should come on, blink off then stay on when you turn the key from off to run. Should stay lit as long as you don't start it.

To my knowledge ABS should have nothing to do with the stalling, but I know very little about how it's powered and what not.

Do you have bad hearing? Not being a jerk, just that normally the pump can be heard pretty clearly as long as there isn't a ton of ambient noise. My hearings not that great and I can hear it ok. May help to stand outside the truck and turn the key while you are as close to the tank as possible.

I would test pressure at the fuel filter, and replace it while you are there if it hasn't been done recently. On principle I'd stay away from Fram. Wix is usually pretty good stuff, and relatively cheap.

correct. CEL comes on, blinks, and stays on as long as i dont start the truck

ABS is just another code ill deal wiht

my mother would say my hearing is horrible, but i think its ok. the truck is lifted and we live close to a freeway, so i might wait til the wife gets home or later tonight to listen for the fuel pump.

going to go buy a pressure tester and new filter now.

 

[jteck10]

It sound electrical to me. 30 seconds restart is a little quick for an over heated pump to start working again.
The wires for the injectors at the tbi are suspect too. the insulation cracks and flakes away.
A visual inspection of the injector spray while running, should have a nice cone shaped pattern, with no gaps.
While engine running wiggle the plugs at the distributor, and the fuel pump relay on the firewall.

i'll try that today as well.
when i sent that video up above, i noticed the injectors were spraying, but not in a cone shape. the cone shape came when i hit the throttle

 

[Wes Harden]

They may be a little dirty, were the injectors new or rebuilt when replaced? Shouldn't stall the truck out unless the air/fuel ratio is really bad. Enough to cause tip/bog stall.

 

[jteck10]

When i swapped a new thermostat in with the water pump about 2 weeks ago, i put a 180 degree tstat in, instead of the 195 oem one
i wonder if that is messing up the computer somewhere for my fuel level and mixture and whatnot?

to try and help it, today i'm going to try the below :
- test fuel pressure at filter
- new fuel pump relay
- new fuel filter (replaced it in January of this year)
- swapping back to a 195 degree thermostat from a 180
- oil pressure switch ? (for the hell of it, since i'll be all up in there checking the plugs)

 

[jteck10]

They may be a little dirty, were the injectors new or rebuilt when replaced? Shouldn't stall the truck out unless the air/fuel ratio is really bad. Enough to cause tip/bog stall.

they were new.
wonder if the new tstat from 195 to 180 is messing that up?

 

[dyeager535]

correct. CEL comes on, blinks, and stays on as long as i dont start the truck

ABS is just another code ill deal wiht

my mother would say my hearing is horrible, but i think its ok. the truck is lifted and we live close to a freeway, so i might wait til the wife gets home or later tonight to listen for the fuel pump.

going to go buy a pressure tester and new filter now.

Borrow one from AutoZone. No reason to need one frequently enough to justify purchase. IMO.

 

[dyeager535]

Don't replace parts for the hell of it. New is not necessarily good. Pump relay and oil pressure switch are easily tested, do so and understand how it all ties together so you dont waste money and you feel confident you know what ISN'T the problem.

Colder t-stat is pointless and certainly doesn't help matters. May not hurt, but it's a variable that is unnecessary.

 

[jteck10]

Don't replace parts for the hell of it. New is not necessarily good. Pump relay and oil pressure switch are easily tested, do so and understand how it ties together so you dont waste money and you feel confident you know what ISN'T the problem.

Colder t-stat is pointless and certainly doesn't help matters. May not hurt, but it's a variable that is unnecessary.

good call
going to go this route instead

1. test pressure at fuel filter from gas tank. i should be at 10-13psi from what im reading?
2. install new fuel filter
3. test fuel pump relay with multi-meter

 

[Wes Harden]

180 t stat will make it run rich. shouldn't effect much on the short term. It could cause the cat to block up.
Something is changing while you drive, why I suspect electrical, since it runs well in driveway. Have you tried power braking ?

 

[dyeager535]

9-13psi is GM spec, but most say at 9-10 they don't run as well.

I'm not sure about that vintage, is the AC relay the same as the fuel pump one? If so they can be swapped. Easy test. But turning the key to run and hearing the pump run proves the relay works. No meter needed. The connectors are sealed anyway, no way to test without puncturing the wire jacket and that's a bad idea.

You can unplug the relay while it's running, if it keeps running it proves the oil pressure switch works. Unplug the switch, if it starts the relay works. Being intermittent it's likely going to be hard to pin down unfortunately...just because one or both work at that time, doesn't mean they do all the time. But if you test and the pressure switch and relay work at that time, you know it stalling isn't because both of them are bad.

It is possible for one to have failed and one to be intermittent. Unlikely, but possible. Easy to rule out.

FWIW the '88+ c/k's used the oval relays (which I believe yours is?) and not that long ago were plentiful in the wrecking yards. Not bad to have around as a spare, and should be dirt cheap. Those seem to be exceptionally good relays. I don't frown on buying parts, but that vintage, I'd rather have used GM than the stuff on the market now.

 

[jteck10]

180 t stat will make it run rich. shouldn't effect much on the short term. It could cause the cat to block up.
Something is changing while you drive, why I suspect electrical, since it runs well in driveway. Have you tried power braking ?

got it, i may swap it back to 195 then once i do some other testing.
anyway to test the cat? mine looks super old

 

[jteck10]

9-13psi is GM spec, but most say at 9-10 they don't run as well.

I'm not sure about that vintage, is the AC relay the same as the fuel pump one? If so they can be swapped. Easy test. But turning the key to run and hearing the pump run proves the relay works. No meter needed. The connectors are sealed anyway, no way to test without puncturing the wire jacket and that's a bad idea.

You can unplug the relay while it's running, if it keeps running it proves the oil pressure switch works. Unplug the switch, if it starts the relay works. Being intermittent it's likely going to be hard to pin down unfortunately...just because one or both work at that time, doesn't mean they do all the time. But if you test and the pressure switch and relay work at that time, you know it stalling isn't because both of them are bad.

It is possible for one to have failed and one to be intermittent. Unlikely, but possible. Easy to rule out.

FWIW the '88+ c/k's used the oval relays (which I believe yours is?) and not that long ago were plentiful in the wrecking yards. Not bad to have around as a spare, and should be dirt cheap. Those seem to be exceptionally good relays. I don't frown on buying parts, but that vintage, I'd rather have used GM than the stuff on the market now.

thats a huge help, thanks!

the fuel pump relay is oval, correct

i have some testing to do here, hoping for the best

 

[Wes Harden]

install a pressure gauge (0 to 10psi) in the o2 sensor bung, warm up engine and cat, @2000 rpm you want less than 2.5 psi.