Pulled most of my hair out!! No clue where to start!

[shaggytx]

93 Chevy C2500, 5.7L. 4 speed w/ granny. My engine ran, spun a main bearing. Swapped block & heads out of another truck, I ran it first. I know #1 TDC, timing mark on HB & Dizy are all on. I have fire, and fuel. I think its flooding out. If I leave it alone for a few hrs, it wants to crank, sounds like it almost does. Then it just turns over. Strong fuel smell, seems like its spraying to much fuel. Any tips, test, specs? Ive been at this point for almost a month, I'm out of ideas, time, & now hair! :mad1: Desperately need her back on the road. Thk ya'll for your time, & feed back.

[EagleMark]

That's a tough nut to crack!

Flooded EFI engines are a pain to get running again. If you are absolutely sure you are timed right, not 180 degrees out? Then pull plug wires off injectors, wide open throttle and see if it fires, if not while WOT cranking spray a little shot of starting fluid in. Notice I said a LITTLE!!! This stuff can hurt a motor, little bit, little bit little bit. If that don't work you need to check spark again and check timing again. HTH!

When done and running and cleared out? Replace the O2 sensor because it's ruined!

[Six_Shooter]

You don't need to disconnect the injectors, just holding the throttle wide open while cranking will put the ECM in clear flood mode.

[jameslleary]

I would check 5 and 7 plug wires...they are easy to cross, I do it all the time! :innocent2:
And, not for nuthin, but i have not heard of an efi truck flooding, unless the O rings in the throttle body are shot, then it wil dump fuel into the intake.

[EagleMark]

You don't need to disconnect the injectors, just holding the throttle wide open while cranking will put the ECM in clear flood mode.That's the theory but it Still pumps fuel out injectors? I think less, but not zero.

[Six_Shooter]

You don't need to disconnect the injectors, just holding the throttle wide open while cranking will put the ECM in clear flood mode.That's the theory but it Still pumps fuel out injectors? I think less, but not zero.

Close enough to zero, to isolate a problem.

Back when I converted my '85 Jimmy to EFI with a hybrid 660 and turbo, I missed hooking up the ground wire to the TPS and the ECM thought it was in clear flood mode, it would not fire at all.

[JeepsAndGuns]

Stupid question, hope you dont mad by me asking. But are you sure the replacement engine was another 350 and not a 305?

[shaggytx]

Thxs for all the reply s guys. I think i found the issue.
firewall dont know why, but something
70psi 8 7 65psi said just check it. Compressions off.
60psi 6 5 70psi I dont know how or why. I cranked it
70psi 4 3 65psi in the truck it was in, no problems.
60psi 2 1 60psi Bought the truck, next day pulled it out.
front end

[shaggytx]

I wasnt sure on the flooding. Ive been around these motors w tbi 13yrs now, & never noticed it spray like that.
Not totally sure on it being a 350, didnt even think to check it. I was told it was, the truck it came out of is a 93 gmc 1ton 4x4 & calls for a 350. I assumed it true. I never messed with the heads, put a new timing chain, oil pump, my intake, tbi, dizy, front/rear seal, oil pan, valve cover, intake gaskets on it. Dropped it my truck.
Any ideas on how comp droppped? Isn't supposed to be around 150psi w/ 20 psi max flux?

[shaggytx]

Another thing on the fuel.
When I was ready to 1st crank, I was 180 out. Chgd it. Gettting fuel, no spark. While playing w it, I unplugged fuel pump relay & fuse out. It still was shooting fuel. I had to unplug pump back at the pump to stop it while turning over. Got spark back. Plugged everything back up, then got fuel out of the line to tbi, but not through injectors. played w/ it, now i'm back to having both.

[EagleMark]

I have no idea how you can pull a fuel pump relay and still get fuel? You must have pulled the wrong relay, that's probably why you had no spark.

Timing chain could be off, that would make it not run and give low compression, intake mainfold change could be a vacuum leak, vacuum leak causes an engine to run RICH!

Never saw it spray like what? Need to check fuel pressure at this point. What is it?

Turn key on, does fuel pump run for couple seconds then shut off? Key off. Pause..... Turn key on and watch check engine light, does it come on,blink and then stay on? Turn key off... pause... watch injectors while cranking engine over, do they spray.

All you did was play with things and now you have fuel and spark? Look for connection issue, could be anywhere with an engine change.

You pulled distributor, rotated 180 and got no spark? Was distributor at least snug? EST module in distributor grounds through the 2 mounting screws to dist, dist needs to be snug if totally claen surface to ground or tight in not clean connection to block.

Pull plugs. Are they soaking wet? If so crank over motor to blow them out, Couple squirts of motor oil in each cylinder, crank over a few times, just tap, tap tap trying not to blow oil out, recheck compression. I do not know if washed out rings from flooding can cause compression to go that low, but it does lower it. Is compression back up? Insatll new plugs and try. In the end this will ruin a good O2 sensor but yours may be soaked and shot already.


Another thing on the fuel.
When I was ready to 1st crank, I was 180 out. Chgd it. Gettting fuel, no spark. While playing w it, I unplugged fuel pump relay & fuse out. It still was shooting fuel. I had to unplug pump back at the pump to stop it while turning over. Got spark back. Plugged everything back up, then got fuel out of the line to tbi, but not through injectors. played w/ it, now i'm back to having both.Normally if you don't get spark you don't get fuel. The ECM fires injectors when it gets a signal from EST in distrbutor that controls when to spark.

HTH!

[Six_Shooter]

Depending on how the fuel pump is wired (there are a few variations) the fuel pump can still be energized from the OPSU.

I have seen some ICMs fail, where there will be no spark, but still provide ref signal to the ECM. They don't usually work after "playing" with them though.

[EagleMark]

What's an OPSU?

[Six_Shooter]

Oil Pressure Sending Unit.

[shaggytx]

Try this agian for the 3rd time.
Only 1 relay on ps firewall, cover says fp relay, fp fuse

Did the key test, dizy thing & pulled plugs b4 I ever found u guys. Key test checked out, playing the dizy is what got me back to having fuel & spark. plugs were soaked.

Intake seal leak wouldnt drop comp like that. timing chain I normally dbl & triple check myself b4 cover. went back & quad checked, should be on.

[EagleMark]

Oil Pressure Sending Unit.
Ahh yes, the double redundant system that doesn't look like it would work the way it's wired... it's one of the things I remove when doing a harness for conversion...