White smoke / pools of gas in intake (84 Crossfire)

[nellis003]

Hi all,


I just bought my first C4 - I've had C3s before but found a 1984 Crossfire Corvette project and thought I'd try to get it running.


The car sat for six years before I bought it, and when I got it started there was a lot of white smoke coming out the tailpipe. I figured it was a bad head gasket, because the smoke looked like coolant smoke. But when I did a compression test, I got around 140 in each cylinder. Most of the sparkplugs were wet, black, and smelled like gas.


So I removed the crossfire setup, and found pools of gas sitting in the intake. Raw gas is getting in there somehow.


My questions are:


Is there a way to diagnose where the leak is? I'm not sure if I should try replacing the seals on the throttle bodies or the injectors themselves.


Could this be causing the white smoke, or is that a separate issue?


Thanks for any input.

Nick

 

[Hot Rod Roy]

Need more details. I've got more questions than answers:

Is the fuel six years old, or have you purged all the old gas?

Did you change the fuel filter? That's a good time to purge the fuel line and check the fuel pressure.

Pump fresh fuel thru the fuel line by putting a hose on the line at the filter, then turning on the ignition to actuate the fuel pump. Inspect for crud in the fuel.

Put a straight piece of fuel line in place of the filter, with a tee fitting in it to connect to your fuel pressure gauge. You should have between 9 & 13 psi. Don't leave this in place very long, since you don't have a fuel filter during this test.

How much were you able to drive the car before tearing it apart? How did it drive?

What did the spray pattern from the injectors look like? They should have nice, even conical spray patterns, and matched from L & R injectors. Use an ignition timing light (strobe) to get a good look at the spray patterns. (A cool feature of the Cross-Fire engine.)

Is the ignition system in decent shape? Sounds like you might be ready for new plugs.

Don't remove the throttle body injectors "TBI" from their mounting plate unless absolutely necessary. This will foul up the critical balance adjustments between the two injectors. Have the TBI adjusters been previously tampered with, or are the adjusters still welded into position from the factory? (I have 240,000 miles on my '84, and they're still welded.)

If you don't have the Factory Shop Manuals "FSM" (two books), get them. You'll learn to appreciate them! Don't waste your money on the cheap books. If you're not afraid to jump into a Cross-Fire dismantle project, you've already surpassed the cheap books!

 

[xfirez51]

Hi all,


I just bought my first C4 - I've had C3s before but found a 1984 Crossfire Corvette project and thought I'd try to get it running.


The car sat for six years before I bought it, and when I got it started there was a lot of white smoke coming out the tailpipe. I figured it was a bad head gasket, because the smoke looked like coolant smoke. But when I did a compression test, I got around 140 in each cylinder. Most of the sparkplugs were wet, black, and smelled like gas.


So I removed the crossfire setup, and found pools of gas sitting in the intake. Raw gas is getting in there somehow.


My questions are:


Is there a way to diagnose where the leak is? I'm not sure if I should try replacing the seals on the throttle bodies or the injectors themselves.


Could this be causing the white smoke, or is that a separate issue?


Thanks for any input.

Nick

Xfire is wet manifold. injectors could be old and dripping.

 

[nellis003]

Roy - thanks for the input. I'll answer as much as I can.

Is the fuel six years old, or have you purged all the old gas?
--It's six years old.

Did you change the fuel filter? That's a good time to purge the fuel line and check the fuel pressure.
--Haven't changed the filter or checked pressure.

How much were you able to drive the car before tearing it apart? How did it drive?
--As soon as I saw the white smoke, I kept running the engine to the bare minimum - I was positive it was a bad head gasket, so I didn't want to do any damage.

What did the spray pattern from the injectors look like?
--Didn't think to look - again, I was sure it was the head gasket.

Is the ignition system in decent shape? Sounds like you might be ready for new plugs.
--Def going to need new plugs. Otherwise ign system seems fine.

Don't remove the throttle body injectors "TBI" from their mounting plate unless absolutely necessary. This will foul up the critical balance adjustments between the two injectors. Have the TBI adjusters been previously tampered with, or are the adjusters still welded into position from the factory? (I have 240,000 miles on my '84, and they're still welded.)
--To my eye, it doesn't look like any of the TBI setup has been tampered with, but then again this is the first time I'm working on one of these systems. Someone has obviously done some work on this engine before - several components have been painted in a way that would require them to have been off the car.

If you don't have the Factory Shop Manuals "FSM" (two books), get them. You'll learn to appreciate them! Don't waste your money on the cheap books. If you're not afraid to jump into a Cross-Fire dismantle project, you've already surpassed the cheap books!

Thanks again for the input. I'm used to working on older, carbureted engines, so once I saw the white smoke I just figured it was a head gasket and didn't bother to do any other checks. Lesson learned.

Nick

 

[nellis003]

Xfire is wet manifold. injectors could be old and dripping.

I've already removed the manifold - is there a way to check for bad seals? When I drained the oil, there was no sign of coolant either.

Thanks,
Nick

 

[xfirez51]

I've already removed the manifold - is there a way to check for bad seals? When I drained the oil, there was no sign of coolant either.

Thanks,
Nick

If TBIs are installed, you can key ON and energize the fuel pump. Then watch to see if injectors drip.
any of the plugs look steamed? How about head gaskets? What do they look like?

 

[geekinavette]

White smoke = coolant is getting into the cylinders. My '84 had this issue when I first got it. Turned out the heads had cracked and someone attempted to repair the cracks (unsuccessfully).

 

[nellis003]

Update

Hi all,

Well, I kind of went all out in chasing down this issue. The compression test was good on all cylinders, but since I had a gasket set and some time, I tore the engine down and put in new head gaskets. I also replaced both injectors, and when changing one out noticed that the nozzle end had been smashed pretty good. And one of the injector wires was hanging together by one single strand.

Long story short, I put in all new gaskets, new injectors, buttoned up some wiring issues, and got it all back together... only to have it smoke just as bad as before.

I'm convinced this is a fuel issue. I drained all the old fuel out before engine disassembly and put in fresh gas, so I don't think old gas is the problem, but it does look like the injectors are DUMPING gas into the throttle bodies. Both have a nice-looking cone sized spray, but a ton of gas comes through while cranking. So much that I can disconnect the injectors from the harness and the car will start right up and run for a few seconds with no gas coming in. With the injectors connected, she's VERY hard to start.

So, what would cause the injectors to throw that much fuel? In comparing my engine to photos and diagrams from the net, I can see that the EGR solenoid is gone. Just completely missing, and the hoses have been plugged up. Would this cause problems like I'm having?

Also, does anyone want to buy a 1984 Corvette? Fun father/son project, REAL cheap.

Thanks,
Nick

 

[nellis003]

Any thoughts on this?

 

[xfirez51]

Any thoughts on this?

When you tore motor down, did u check head and block for cracks? Does it smoke all the time or is it
worse at idle and decel?