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TPI Ignition Problems, Need Help ASAP

Hossbaby50

Hossbaby50

3/4 ton status
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Location
Peoria, AZ
I am having ignition problems with my TPI setup. I need help ASAP, I need to get this truck on the road today if possible.

I pulled my distributor to replace my pickup coil and my reluctor ring (had a small crack). I marked everything when I pulled it out. It still didn't seem to want to drop in in the same place. So I manuallly found TDC and set the distributor. (I found TDC on the balancer and with a spark plug gauge)

I start the truck and timed it to 8* BTDC. The motor runs fine as long as the timing circuit is disconnected (like when you time the motor) When I turn the truck off and reconnect the circuit and start the truck it runs horribly and then dies. I can't figure out WTF is going on.

I replaced my module, ECM, and EST but none of it helped any. I am not 100% sure my spare EST is good but I know that the module and ECM are good.

I went looking for loose wires and things but I am at a lose. I can't figure out anything to get this thing to run right.

Why would the motor idle fine with the computer timing disconnected and not with it connected. It ran perfectly before.

Thanks
Harley

P.S. The setup is a 88 MAF TPI on a stockish 350. Painless harness.
 
Set the timing to the stock TDC (0deg) and go back from there. I think I have mine set back to around 4* BTDC but I run 89 or higher only, and that's allot less than 8* BTDC (remember, this isn't a carbed engine....)
 
If the pickup coil was bad though it wouldn't run at all correct? This is a brand new AC Delco pickup and the motor runs fine with the timing switch off.

Once I start the truck with the computer controlling everything it won't run for crap and dies so I can't see what the computer is trying to time the motor at. It was setting it to about 16* back when I checked it once a few months ago.

I am told that with TPI your timing should be in the neighborhood of 6-8* BTDC with the timing switch off.

Harley
 
Yes, your right. I was thinking about TBI for whatever reason. Please ignore the CK5 Goober behind the curtain. /forums/images/graemlins/yikes.gif
 
According to Corvette Fever, if it runs without the timing bypassw wire connected, but doesn't with it connected, the module is toast. That was the ONLY test mentioned in the article for the module being bad.

Don't have the specifics in front of me, but under 400RPM with the wire hooked up, the module handles spark, over that, the ESC(?) takes over, and if I've got that right, must mean only one portion of the module "fails", however it handles the spark with the timing wire connected.
 
Test out of the Camaro manual starts off checking to see if the ECM is seeing RPM while the engine is cranking. If you can't scan the ECM, this flow chart won't help you.
 
It has to be seeing the RPM since it starts with the timing wire connected. It tries to run but it just won't keep the truck running. It bumps up to 800rpm and then starts to sputter and then die.

I replaced the module already. It didn't change anything. I can't for the life of me figure out WTF is going on. I already replaced the ECM with one I know works.

I also replaced the ESC but I don't know for sure that the one I swapped in was good.

Harley
 
No, that doesn't prove anything if it starts, since the module handles spark under 400RPM all by itself, even with the timing wire connected. Once it exceeds that, the method of operation changes, and that is where they apparently fail.
 
Well, just glanced at the service manual, to see if there is anything else that helps you.

Defective MAF may cause hard start or stalling after start. Disconnect the MAF connector and try to start it. If problem is gone, check/clean all connections regarding MAF, if no problems there, replace MAF. Personally I wouldn't replace the MAF unless I tested some more, there are specific tests for MAF voltage that are easy.

Basically, the RPM test sets you on a path either to spark, or fuel. (check fuel pressure at key on the one side of chart)

The other test again references RPM when another test is performed, and at that point, if RPM is indicated, faulty connection or ignition module, if no RPM indication, CKT 430 is open, shorted to ground, or the ECM is toast.

IMO NONE of the tests are concrete proof that one component is the problem, however they can get you close enough to test individual components and connections.
 
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