It's seems like the TPS on the Accel Pro-ram I just installed is basically non-existent. When it was running and I step on the gas even at a relatively usual rate the engine died like it had no fuel. Idled great though. I checked the TPS voltage manually at the wires, but I got some wierd readings. Should they be like GM(.5-4.5 or so) readings or will they be totally different?

Now when I try to start it it fires up for a second and dies like the initial start enrichment works, but maybe the TPS isn't taking over after that? Could it be a bad TPS? It does this every time now - fires up for a second and dies.

This is so frustrating!

Thanks

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88 firebird formula
350 Vortec, Accel Pro-Ram MPFI
214int/224exh, .471int/.491exh
Edelbrock headers
T56 - SIX-speed
open 3.73's
3 inch Flowmaster catback
I love pissing those LS1's off

Old time with TBI - 13.9 @103mph, 2.6 60ft

My Formula

 

Unplug the TPS and the computer will use a preprogrammed voltage. If this makes the car run, change the TPS. Yes, the TPS should be around .45 to .5v. If this doesn't make the car run look elsewhere. Are you getting fuel? Or are you missing spark?

 

I unplugged the TPS and it did the same thing. It starts up for a second and then dies. Same every time. SEems to be getting fuel and spark, but only while cranking. Coil checks out good and I tried another coil also. Don't have another TPS.

Any ideas as to why an engine would start while cranking, but won't run after?

 

Oil pressure sending unit...

The FP gets its juice through the FP relay during startup, then after the engine is running, it gets it through the OPSU. There should be 2 OPSUs on your car: one for the gauge, and one for the FP; one under the dist, and one right above the oil filter (as they come from the factory).

TPS voltage should be similar to stock values at idle and everywhere else. Also IIRC from a Pro Ram I worked on once before, the connector pinout is different from stock; you may have to re-arrange the wires to get it to run right. I don't remember the exact pinout; but the harness should have a pink wire which is +5V, a black wire which is ground, and some other color (blue I think) that is the signal to the ECM.

If you measure the TPS, there will be a constant resistance between 2 terminals; one of those 2 goes to the +5, the other 2 ground. Then there will be a terminal be with resistance between it and both others that varies as you move the throttle; that one is the wiper. The one of the first 2 that has low resistance between it and the wiper at idle is ground, and the one with high resistance to the wiper is +5. Obviously the resistances should "swap" as you move the throttle, such that at WOT it should be low from wiper to +5 and high between wiper and ground.

What computer are you using?

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"So many Mustangs, so little time..."
ICON Motorsports

 

Are you absolutely sure you're getting fuel and fire? Have you pulled a plug wire off and grounded a spark plug from it to test fire it? Do you smell fuel? Is your fuel pump electric or mechanical?

 

I thought OPSU also, but this is a new DFI system totally independent of what was on the car from the factory. The fuel pump primes when I turn the key. I'm positive the car is getting fuel and spark as I'm cranking because it literally starts the engine, but once I let the key back to "run" it quits.

Is there some sort of relay connected to the distributor 12 volt supply that might go bad and only supply power to the dist. only during cranking and not in the "run" position?

 

Have you put a voltmeter on the power to the distributer plug after it dies to see if you've lost power there? Have you unplugged the computer from the distributer to see if it stays running?

 

Is the timing right? Have you tried retarding it?

 

Yes, there is "some sort of relay"... it's called an Oil Pressure Sending Unit.

If you're using the car's original wiring to the pump, then you need to check the OPSU. The ECM only commands the FP to run for a couple of seconds when you turn the key to "On", and then after that, only while the key is in "Start". If your OPSU is not hooked up, then as soon as you let the key back off of start, the 12V feed from the relay will go away and the engine will die.

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"So many Mustangs, so little time..."
ICON Motorsports

 

This is totally new wiring on everything that the computer controls. A whole new harness is in the car for fuel and spark management, so the OPSU does not even factor in. New fule pump and wiring.

The timing is at the same exact position it was when the car was running fine.

This is exactly what happened when the car started acting like this...

I left the ignition on to check the TPS voltage. I went and got the voltmeter while the ignition was on without the car running(took me about 5 min to get back to the car). I tested the TPS and got some wierd readings, but until I can call Accel I won't know what they should be. Could crossing the TPS wires without knowing have fried something? DFI ECM seems fine, I can still comunicate with it through a laptop.

Could leaving the ignition on without the car running for so long have fried something? I also have to leave the ignition on without the car running to load new programs into the DFI computer so there's a lot of time where the ignition is on without the car running. I know this could hurt your coil, but can it hurt anything else?

 

Unfortunatley I've had to treck back to school for the week so I'm screwed as far as working on the car until friday. I'm thinking the ignition is not getting power after I set it to "run". I'd test it now, but I'm away from the car now .

The fuel pump seems to be running while in the run position because when the engine dies the fuel pump is still running.

Any more ideas or details as to how the the functions of "Start" and "run" work? Thanks.

 

Get a third generation Camaro repair manual. Most of these manuals have a wiring diagram in the back. Maybe the manual can tell you what wires affect the start and run. If not, at least you'll have a new manual if you have any other problem it can help you with - most of the info in them is generic to cover more setups than you'd think.

 

I don't know too much about those accell DFI's but does it have an IAC? It sounds like what happens when my IAC plug falls out....(Still gotta change that &^%(&*% wiring harness and get the $#%&*&% duct tape off of it!)
Corry

 

Apparently 2.4 or so is right for WOT. This would mean my TPS was wired backwards by Accel. That should solve my acceleration enrichment problem, but my car still won't start.

An IAC is present, but it won't start even if I open the throttle blades up, which it should. I'll have to wait and try and friday .