TBI is Dying

[JoePolo]

I bought an 89 Suburban with a 350 TBI. The second I bought it, fired it up and went to leave the fair grounds (bought at a swap meet) and it died. Took a bit to get going again, got it going then drove about another 1/2 mile and died while driving. Pulled over and got it going again. Then drove 2 hours home with no issues at all.

Until today…..

Went to the smog station (about 3 miles from my house). It died a few blocks away from the station and started again. Then once it got to the smog station it ran and idled for a while then from that point on, it wouldn’t stay running for more than a minute. So I took it back and limped it back to my garage.

It will do it idling or driving, takes 30 seconds to a minute. It will restart every single time with a key cycle as if nothing was wrong then do the same thing again. If I try to start it without a key cycle it won’t restart.

Any ideas of where to start. When running both injectors are firing, at first they weren’t (unplugged and plugged them back in and they both work every time now) but still having the same issue. I’m baffled.

[raggedjim]

Happened to my '94, it was the fuel pump. Not saying yours is the fuel pump but same exact symptoms.

Good luck, Rg

[sntrym95]

You need to log data to find out if a sensor is crapping out. You can also test fuel pressure but need to add an inline gauge. Check for codes using a paper clip. There is a sticky on this forum on how to do it.

[JoePolo]

Originally Posted by raggedjim

Happened to my '94, it was the fuel pump. Not saying yours is the fuel pump but same exact symptoms.

Good luck, Rg

Exact same symptoms is a pretty good starting point. I’ll check fuel pressures as it happens and also change the fuel filter as a just in case.

[Palf70Step]

How old is the fuel? You could be getting some junkin the system. As others say test fuel pressure and check fuel pump.

[raggedjim]

Originally Posted by JoePolo

Exact same symptoms is a pretty good starting point. I’ll check fuel pressures as it happens and also change the fuel filter as a just in case.

I hope it's not, dropping the tank is a bear.

[JoePolo]

Originally Posted by raggedjim

I hope it's not, dropping the tank is a bear.

I have a lift and a transmission jack so won’t be too bad but also hoping I don’t have to drop the tank.

[JoePolo]

Originally Posted by Palf70Step

How old is the fuel? You could be getting some junkin the system. As others say test fuel pressure and check fuel pump.

Fuel is fresh 91 octane after the 2 hour drive home it needed a tank haha

I’m also gonna test ignition switch I bought one the key cycle has me thinking it’s ignition more than fuel but I’m still going to test the fuel system.

[JoePolo]

Changed the ignition module and the coil and so far so good. Is there a source for replacement pigtails for the module? Both the clips were broken off when I got to it.

[raggedjim]

Good deal, I've been lucky and have never changed mine. I probably should get a spare one, I've got 230,000 on it!

Rg

[hatzie]

Originally Posted by JoePolo

Changed the ignition module and the coil and so far so good. Is there a source for replacement pigtails for the module? Both the clips were broken off when I got to it.

The part numbers for the Metripack plugs are in the GM wiring diagrams.
Before replacing parts I'd spray the connectors with Caig Deoxit D5, plug them in and remove them several times, and spray them down again to rinse out any corrosion you loosened up.

Your symptoms sound like you've got a fuel pressure/delivery issue.
Put a gauge on it and check prestart, idle, and loaded pressures along with how long it takes for the pressure to bleed back down when you turn off the key.

The TBI fuel pressure regulator is inside the throttle body assembly. There's a TBI pressure regulator modification thread on the third gen F-body board with disassembly pictures.
https://www.thirdgen.org/forums/tbi/...regulator.html
If the fuel pump has never been changed... the polymer mesh pickup sock in the tank may be coming apart and blocking the pump inlet.