Looking at a car with crossfire. He parked the car and did a brake job on it. After he got done he went to start the car and it won't start unless you hold it floored. He thought it was the computer and replaced it and it did not change a thing. Any body have an idea. About to rip the intake off and go carb!

 

https://www.thirdgen.org/techbb2/sho...ssfire+AND+iac

Read in this link that his problems was the FP. Can I just check the voltage to see if the pump is bad? Should be a check point in the engine compartment? I have the Helms manuals on the way, just asking questions before they get here to try to get it running ASAP.

 

Since the ignition was mostly original and over 20 years old. We rebuilt the distributor, new ignition module, pickup, cap, rotor, rotor button, plugs, wires, everything. Tried ECM. Changed the FP, wasn't holding pressure so it was getting weak. All of this work and it didn't change a thing on how it is reacting. It is getting fuel, and it has spark. Put a plug in a wire and it definitely sparks.

Turn it over, it wants to start and dies. Then crank forever and it won't fire at all. Hold it floored and it starts running barely but is backfiring through the crossfires. Last thing I can think of is the Eprom being bad.

 

do you have the correct firing order? also sinc eyou have to hold the throttle open it sounds like its running rich.l

 

Make sure all the spark plug wires are going to the right cylinders. I had a similiar problem with my LO3.

 

Could have a bad timing chain and gears. If thats the case it could have jumped time. Disconnect the tan wire(if a crossfire has a tan wire) that goes to the distributor then check your timing.

Steve

 

Can you use a timing light pointed into one of the TB bores to see if you're really getting fuel during and after crank? Specifically, do you see fuel without having to have the pedal to the floor? And, do you see the same patterns after the first fire *and* the later crank-but-no-start-without-flooring-pedal fire? Maybe there's some sort of obstruction in the fuel system such that the fuel isn't flowing freely. In this case, you'd be able to see the right pressure. You just wouldn't be able to flow very much at that pressure..... This might also help explain why you experience a quick start followed by nothing until the car sits for a while....

Good Luck!

 

I triple checked the firing order and the timing setting before the change of the distributor...It was right on and all correct. The distributor rotates while cranking. The timing chain should still be in one piece.?.? Can't get it to run long enough to get the timing set again now.

 

1981TA The fuel is flowing out of the injectors the same before and after fire. Holding if floored I think shuts the injectors off until it fires or hits a certain RPM. Flooded mode in the programming.

 

Doh!!

I thought you had to hold the throttle open to get "enough" fuel to keep it running. I didn't realize this was a "too much" fuel problem.

As was mentioned in the other post, I'd make sure your coolant sensor is reading correctly. While you're at it, I'd also check the MAP and TPS sensors. If the ECM thinks the engine is cold due to bad coolant sensor, it will add fuel. If the ECM thinks MAP is high, it will add fuel. (While doing the "brake job", the guy didn't disconnect any vacuum lines under the hood, did he?? ) If the MAP sensor is good but disconnected, it's going to tell the ECM to give the engine the equivalent of full throttle fuel...... Even if the sensor is connected to "something", make sure it's connected to the manifold or TB on the "manifold side" of the throttle body. I'm thinking back to when I'd mistakenly connect the vacuum advance line of an HEI to the wrong port on a Q-jet.

 

did you have the #1 cyl at TDC and then line the rotor up as close as you could to the #1 spot on the cap when you put the dist. in. this sounds soooo much like the timing is off. if you did try turning the dist. a bit while cranking it over until it fires up.

 

I checked all the vaccum line routing and locations to verify they are hooked up. The only vac line unhook is the one to the air cleaners, since we have the air cleaners off. Would the air cleaners being off cause it not to start? I am grasping for straws here.

 

Yeah I verified the TDC was pointed at the #1 cyl. Plus no matter how I adjust the dist it won't fire and run. I think I will get out the chip burner and see if I can burn a new chip for his ECM. It is the only thing left that would make timing not work.

 

try disconecting the EST wire then and try to start it and see what it does. that would make it so the computer doesnt mess with the timing.

 

Remember, it's not just that they're hooked to "something" but that they're hooked up to the *right* "something". If you follow the MAP sensor hose to the engine, where does it connect? Make sure it's not Tee'd to one of the lines that isn't hooked up. When the engine is semi-running, do you feel any vacuum at these lines? It might be a good idea to temporarilly plug them just to eliminate any possibilities...

As a quick test, you might try disconnecting the electrical connector on the MAP sensor. ECMs will *usually* default to something that will allow the vehicle to start. (ASSuming the MAP sensor is the culprit.) At least it's a quick-and-easy thing to check.

Excellent suggestion! I had a problem with an ESC module once that finally got diagnosed after doing the above. The procedure in the manual was to disconnect the distributor from the ECM at the 4 pin connector. See if the vehicle will start/run. If it does, short the distributor "high" reference signal to the EST signal. If the engine dies, the ignition module or wiring to the distributor is the problem. If the engine continues to run, the problem is on the "ECM" side of things.

You mentioned burning a chip for the ECM. Do you have any way to log ALDL data?

 

I have tried a new MAP, but will disconnect to see if it works. Also I did verify the routing of all the vac lines.

I didn't think of the EST wiring thing. I will try to run it without it on.

The car won't run long enough to check the vacuum produced. It will die within second of barely breathing life.

I just received the helms manual today. Hopefully they have some troubleshooting we can follow.

I have datamaster for the Typhoon only, but friend locally has Diacom which will work for all GM's. Unfortunately he is out of town this week.

 

I did absolutely every peice of advice I recieved thus far. I have went end to end in the helms manual doing tests to check the sensors and wiring.

We have spark at all 8 cylinders. We have fuel at both injectors. The EST signal we have 2.8 -3 volts while cranking. The manual says under 1v for idle and that range for 1800-2200rpm.

My bud with a diacom cable is getting his back on Saturday. So I will be able to datalogg a little and share the files if anyone knows what to look at. I don't know what the baseline number are, but will know if anything is totally out of whack.

Any ideas I have over looked? Fuel, Air, Spark= not running

Triple checked TDC #1 and dist rotor pointed directly at #1.

Blah, going insane, going INSANE. LOL

Thanks for listening.

 

Double checked all the vacuum routing. There is visible gas oozing out from under the TBI.

 

change the TBI gaskets!! It WILL NOT RUN RIGHT if there is a leak there.

 

Turn the distibuor 180 degrees or point it at the number 6 cylinder. After I rebuilt my engine it would start and run with it at the number one cylinder but all of a sudden it would only start and run with the distributor turned 180 degrees from the number one cylinder. (who knows)

 

The distributor is in the right direction.I double checked TDC #1 and the dist was aimed right at #1.

 

Yea replace those TB gaskets!!! If youre getting fuel and spark and triple checked the timing its something to do with getting air.

 

I wanted to get all theories before changing gaskets. Because if he changes the gaskets it will be for a carb and performer intake. Owner is getting really really tired of the crossfire.

Any chance the E-prom is bad. It is the only thing we haven't dealt with and is non returnable item.

 

Have you actually disconnected the EST line while adjusting the distributor? If there is a problem with the ECM controlling spark, disconnecting the EST line will take this out of the equation. There should be a connector on *one* of the wires coming off of the distributor connection. When it's disconnected, it forces the timing to a fixed value.

Just seeing a particular voltage on the EST line won't give you a complete picture. There's actually a waveform sent from the ECM that tells the distributor when to charge the coil (dwell) and when to spark. If the timing of these waveforms isn't right for some reason, you won't be able to tell with just a voltmeter. (Now, if you have access to an oscilloscope, that's a different story.) So, you could be seeing spark. You could also be seeing a voltage on that line. But, the timing of these events could be off by a mile from where it's supposed to be.....

And, I hate to sound like a broken record and repeat what's been said again, but... I would triple check that cylinder #1 is on TDC of the compression stroke with the distributor pointing the the #1 wire. If nothing else, just swap the wires on the cap 180deg just to see what happens. Like you mention, given spark and fuel, you should be getting some sort of operation from the engine....