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Ignition Problems

1K views 10 replies 4 participants last post by  davesmith 
#1 · (Edited)
Had a new race motor built and we are now having ignition problems. The motor is a Boss 302- clone engine, fuel injected, running on an A9P computer, factory harness. The specs off the motor were sent to a guy in Canada who burned a custom chip for us.

The motor runs great up to about 3200 RPM- then starts missing and generally running like crap. Had a complete diagnostic ran on it and I am told everything looked fine. All grounds have been checked and are good.
We have replaced the camshaft, adjustable roller rockers, fuel pump, etc...
As a result of the new motor, we had to put in an after market distributor. Due to clearance peoblems we installed a Mallory 7970404 Distributor. I called Mallory today and they suggested the problem might be not enough coil. He explained that the current coil doesn't have enough wraps to keep up with the new distributor and ignition. I am using a factory/factory replacement coil form Accel.

The Mallory tech recommended we try an "Electronic Coil". Does that make any sense? Is there a difference between the factory coil and an "electronic coil"?

Any other ideas on what mught be causing our ignition problems?

We put a timing light on the motor and checked each cylinder/plug wire to run down the miss. Each cylinder does it, so it has to be an ignition problem.
 
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#3 · (Edited)
Actually the factory coil was replaced last year with a MSD coil, but it is a factory replacement for a 5.0 TFI.

We did some more digging tonight and found that the signal is dropping beteeen the TFI module and the coil. The Mallory distributor had a new TFI on it when we installed it, and has since been replaced with a factory Ford TFI and the same result.
 
#4 ·
was it working fine for a while?

if so it sound like the TFI is taking a dump, or your loosing fuel. check your fuel pressure when it starts cutting out.
 
#6 · (Edited)
The motor has not ran right since we finished it. A stock distributor will not between the fuel rails.

When the Mallory wouldn't work right, we gutted it and replaced them with stock Ford parts.

Fuel pressure is fine and we are not losing pulse or signal to the injectors.

We have the problem narrowed down to an ignition issue. Is there a difference between a factory coil and an "electronic coil"? I had the Mallory tech tell me there was a difference and I just called the engine builder and he aslo said there was a big difference.
 
#7 · (Edited)
Help Is Desperately Needed

Let me run down what we have tried and see if anyone has any other ideas.

Changed camshafts, new set of adjustable roller rockers, new Mallory distributor becase the stock wont fit between the fuel rails, replaced the mallory parts with stock parts, replaced the TFI module, new coil, new fule pump, checked all ground wires, complete wiring harness check, new plug wires, new computer, tried running with and without the custom chip.

This thing is kicking our butts. We have had about 15-20 people try to figure it out and nobody has any ideas.

It runs fine to about 3200 RPM, then starts cutting out.

Fule pressure is about 42 PSI and is constant. No loss of signal/pulse to the injectors.

We put a timing light on all plug wires and are losing signal to every cylinder at about 3200 RPM.

When I checked the wiring harness, I saw a loss of signal strength on a green wire with a yellow stripe on it that runs from the computer to the TFI module and the Coil. That wire has what appears to be an inline resister in it. The wire runs from the computer to the resister and then splits to the coil and to the TFI module.

We already missed the first race of the season becasue of this problem, and we haev about 10 days before we leave for the next race. Any ideas???
 
#8 ·
ignition problem

Just a quick suggestion are you sure that you have the correct firing order. Late model 302 had the windsor firing order 1-3-7-2-6-5-4-8. I know that the motor will idle o.k. with wrong firing order, but will start missing under accerlation. Just something to check it seems like all components have been swapped already.:shaking:
 
#9 ·
Yes- the firing order is set for an HO style. The A9P computer came off of an HO motor, and the cam is also HO order.
Would/could the MAF be causing this problem?
 
#11 ·
Problem Solved!

The problem has been resolved!!!

Thanks to Ford Racing Tech Support- we identifed that there was a red wire on the TFI module that ran and was connected to a 12V constant point and was supposed to be connected to a start only point. We disconnected that wire at the TFI module and it ran great!!!

Saturday I will take off the original Mustang parts and re-install the 90 mm MAF, 42# injectors, and 70 mm Throttle body.

Thanks for everyones suggestions and help.
 
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