94 Bravada wont start now

[thebox_is_here]

My gf's Bravada recently had the fuel pump go out and it required the pump and sender unit to be replaced. Before the pump went the truck started fine no problem, now it turns over but just wont start. Ive checked fuses, distibutor ignition, the only thing i have found is a spark that is not 100% but not bad. Any Help or idea's would be much appreciated.

[ericn1300]

did it ever work after putting the new pump in? check the fuel pressure at the engine. there's a shraeder valve (like a tire valve stem) on the left rear of the engine. you can use a tire guage to check it. did you change the fuel filter at the same time as the pump?

[thebox_is_here]

It has not started since changing the pump but, it is getting fuel we have checked. We even tryed squirting fuel directly into the intake and still it did not start. Could it be the ECU? Also we have not changed the fuel filter. This is really racking our brains.

[ericn1300]

fuel + spark means fire. unusual for an ECM to totaly fail. you can try to read any ECM codes by jumpering the connector under the dash right about where your right knee would be when driving. jumper the two pins in the upper right hand side with a small piece of wire or a paper clip (see pic below) then turn the ign switch to the run position to display the codes

http://s-series.org/albums/album81/O..._WEB.sized.jpg

you might also check the crank position sensor connector to see if that's the problem

[Chris Stewart]

Check the fuel pressure...gotta be around 60 psi.

[thebox_is_here]

Okay, rechecked and fuel pressure it is good. I believe it is flashing a code 12, which is faulty ECU. I also believe that fuel is stopping somwhere between the pressure gauge and the injectors. The plugs were pulled and were dry. So I'm still thinking ECU. Any other idea's?

[ericn1300]

Originally Posted by thebox_is_here

Okay, rechecked and fuel pressure it is good. I believe it is flashing a code 12, which is faulty ECU. I also believe that fuel is stopping somwhere between the pressure gauge and the injectors. The plugs were pulled and were dry. So I'm still thinking ECU. Any other idea's?

code 12 is start of file and end of file. the ecm will flash code 12 three times at the start then flash any codes stored three times each and then flash code 12 three times again after the last code. sounds like the ecm is fine if it's responding.

this post has some good pics of the fuel lines and spider after the pressure test point: http://www.automotiveforums.com/vbul...d.php?t=518850

[Chris Stewart]

After turning the motor over a few times, smell the exhaust tailpipe for a gasoline odor. No odor-no fuel. If you have a strong gasoline odor, likely not enough spark. The ignition coil does get weak after this many years.
Can you hear the fuel pump come on when you turn the keyswitch on?
Exactly how much fuel pressure did you read on the pressure gauge?

[thebox_is_here]

There is a code 12, which is faulty ECU. Fuel pressure is at manual spec. We did try a new ignition coil and no change in spark so I think it is ok. We can hear the pump come on and there is no unburnt or burnt gas smell from exhaust.

[ericn1300]

Originally Posted by thebox_is_here

There is a code 12, which is faulty ECU. Fuel pressure is at manual spec. We did try a new ignition coil and no change in spark so I think it is ok. We can hear the pump come on and there is no unburnt or burnt gas smell from exhaust.

read how to do it here: http://www.autozone.com/servlet/UiBr...3d8018babd.jsp

notice step 5 clearly states that code 12 is not a fault code

did you check the crank position sensor? that's a common cause. the fuel injection will not function without a signal from the crank sensor. . here's how to check it. http://www.autozone.com/servlet/UiBr...3d8018b8a6.jsp

[Chris Stewart]

What's the fuel pressure and how did you check it??

[Chris Stewart]

Bad news fellas...the 1994 Bravada is OBDII.
The good news is an OBDII scanner will likely point to the exact problem.
More bad news...the '94 OBDII was not quite complete and will likely require a repair shop/dealer type scanner like the $$$$ Snap-On unit.

[Chris Stewart]

From our 'ol buddy Blazee:
http://www.automotiveforums.com/vbul...d.php?t=553044
Thanks again Blazee!!!

[ericn1300]

Originally Posted by Chris Stewart

Bad news fellas...the 1994 Bravada is OBDII.
The good news is an OBDII scanner will likely point to the exact problem.
More bad news...the '94 OBDII was not quite complete and will likely require a repair shop/dealer type scanner like the $$$$ Snap-On unit.

the 94 might be an OBDII, dpending on vin number. Shucks, Kragens, and Checkers auto parts stores loan/rent the scanner you need for the OBDII since you can't take it there if it won't start.

looks like the ecm and trouble codes vary by vin number as do a lot of parts on the 4.3, as i found out the hard way. found this cool site: http://www.troublecodes.net/GM/

or go to this link for most makes: http://www.troublecodes.net/technical/

[thebox_is_here]

Well the vin is definitely OBDI. I didn't personally check the fuel pressure but, my gf father checked it against the manual and said it was correct. We havent checked the CPS but we can. The reason I say I am thinking ECU is the Hayes manual says for the model of Bravada I have there is a code 12. I'm ready to throw caution to the wind and try the computer route.