92, 4.3L ran fine until it didnt.

[brettf]

Helpin a buddy out and I've little experience with Chevy TBI systems..

He's got a 92, 4.3l TBI .. daily driver, ran great until yesterday when he came out of the store and now it turns over but no start.

Noticed theres no fuel pump prime going on (cant hear the whine we normally do) when we first turn key on..

FP fuse under the hood is ok, but I measure no voltage to it.

I know the Ignition Module on these things likes to die.. are the ECMs on a truck this old smart enough to notice a dead IGN module and not bother turning on the pump?

Also, I keep getting mixed info on this from the google, IS there an oil pressure switch in the fuel pump circuit on a '92?

thanks for any advice you can offer..

 

[lessersivad]

Well i just checked rockauto and i would say the oil pressure switch is in the fuel pump circuit.

Now as a side note, a couple of days ago I was working on a 1989 GM with TBI and had the fuel lines disconnected. I simply wanted to crank the engine over WITHOUT ignition or fuel. So I jumpered at the starter.

Wellllll, After cranking for a little bit I heard fluid hitting the floor of my garage. Gas was spraying out of the fuel feed line WITHOUT the key on!!

So I would try finding the relay to see if there is any voltage there and possibly find the correct pins to jumper the plug.

Hope this helps.

 

[evilunclegrimace]

Check your ALDL connector and see if it has a terminal in the "F" position (top left) if it does jumper it to the "A" terminal opposite end top right. This will power up the fuel pump if the relay is good and the fuse is good. Listen at the filler neck to see if the pump runs.

And yes there is a oil pressure switch in the circuit.

 

[brettf]

Thanks for the replies.. We're down in the shop muckin with it now..

Of course its friggin fixed itself overnight.. Did nothin, changed nothin since last attempt yesterday evening.. Turned key this morn and it primed right away and runs great..

Now we get to troubleshoot an invisible problem, hah..

 

[lessersivad]

Thanks for the replies.. We're down in the shop muckin with it now..

Of course its friggin fixed itself overnight.. Did nothin, changed nothin since last attempt yesterday evening.. Turned key this morn and it primed right away and runs great..

Now we get to troubleshoot an invisible problem, hah..

Yea, intermittent problems are a pain in the astrological forecast.

You could just do a simple visual inspection to see if there are any "IFFY" spots in the harness. One good place to check, though a pain in the rump roast is right at the fuel pump connector.

A friend of mine dropped the tank, changed the pump, installed everything and 'nuttin'. We jumpered the fuel pump relay connector and still 'nuttin'. Disconnected at the fuel pump connector to see if there was voltage at the connector.

THAT is when the broken wire was discovered.

Now this was on a '98 S10 Blazer but it MAY be worth a shot.

The 'ol 'jiggle test' may reveal a fragged wire also.

 

[Eveready]

This other thread I have been following seems to be a very similar issue. You might want to follow it and see what he comes up with ..

http://www.gmt400.com/threads/no-start-issue.42119/#post-1010783

 

[brettf]

No F pin on the aldl unfortunately, jumped E on the fp relay plug to battery as it looks like that feeds the pump and no pump noise. We do have 12v at fuse durijg 2 sec prime now. Thinkin pump, testin more