false RPM signal

[Hawaiian Turbo]

I was looking at the timing table while cranking and it was going from 500 over to 7500. I presume that is what's causing the hard starting... dumping in fule as if it was really at 7500 rpm. What would cause this? I checked rotor phasing, and it's pretty close, rotor facing at number 1, crank at 52, reluctor in the middle of pick-up. I'm running an MSD 85551,and have the crank trigger for the FAST hooked up to the two pick-up wires from the dist.

Any ideas ? Should I just get a crank trigger and forget about it?

Thanks, Paul

 

[10SV6]

Take and twist the crank trigger wires together. Also try to run them away from postive wires and also the coil wire. If you are using a harness from FAST, there is shielding on the crank trigger wires in the harness. The shielding should be grounded.

 

[Hawaiian Turbo]

I'll try twisting the crank trigger wires together. The FAST harness is grounded, ( I checked that and ignition wires for interfearance) Maybe I should run the trigger wires out of the FAST harness and sheild them.

Thanks, Paul

 

[HighPSI]

Some things I have found for this to occur were 1) Too slow of cranking (ecu sees a signal then times out, then it sees the next signal) and 2) "Noise" on the Crank Trigger wires and 3) Worn distributor gear with enough slop to cause an additional false signal

 

[Hawaiian Turbo]

Cranking doesn't seem too slow, and dist. is brand new, so I think it's the trigger noise. Any suggestions on sheilding them?

Thanks Cal,


Paul

 

[10SV6]

The harness is already shielded and grounded. You should try to twisting the pickup wires and see what happens. Then if that doesn't work, work on getting the trigger wires away from high voltage or high current wires.

 

[Alky]

You're going to fry my FAST ecu trying to fix your problem!!!!!!!!!

 

[Hawaiian Turbo]

That's MY FAST in there.... yours is on the side....... just in case

I tried twisting the wires, and it helped alittle.... now it only jumps up to 4000 rpm. I'll work on isolating the trigger wires from high voltage ones. Thanks 10sv6

 

[bobc455]

I don't know how much it applies here, but I had an HEI with the coil in the cap, and during cranking my RPM signal would go to over 11,000 RPM.

I got an external coil and moved it far away from the pickup wires, and that solved the problem.

Just some food for thought.

-Bob Cunningham

 

[Hawaiian Turbo]

THanks for thinking Bob... my brain is geting fried!!!! I moved my coil and MSD box all over the place. It still jumps up on occasion. I checked the crank reference again with a timing light, it was about 3 degrees off, so I put the FAST ref. to 47, and then the actual matched the target. Has anyone had problems with the mini starters? Maybe my engine IS cranking too slow. Sometimes the engine will turn over twice and then stop. Getting very flustered here!!!!

THanks guys,
Paul