We have a mystery on our hands. The partner car to mine has been in a dead state for many years. EVERYTHING on this car has been replaced (which isn't much, it's a race car) and it still will not fire. We've brought in the best and still can't get it to run.

So, what it comes down to is this:

The car has been stripped of all electronics except the ECM and ICM. So in doing this, is there anything simple that I could be missing? Is there a VATS type security line that needs to be grounded, or a oil pressure switch that could be cutting fuel, etc, etc?

Some details:

It still has a stock computer (with a PROM and several tune options) and basically stock harness but many circuits have been deleted.

Suffice it to say (for now, anyway) that we've exhaustively checked the sources of air, fuel, and spark. We've checked and rechecked the distributer to #1 TDC. Every wire in the harness has been ohmed out and checked for proper voltage (key off and run) and shorts to ground. We can manually force the fuel pump on and have pressure at the rail. Injectors seem to be firing properly but the plugs are usually not wet. Spark verified at each plug.

Before we tear into the mechanicals and look for a bad cam I'm praying there's something stupid that the ECM doesn't like, but hope is dwindling fast.

Check here for info on VATS: www.vatssucks.com

I would start there... if you don't bypass VATS, I would make sure it is bypassed.

I don't want to cloud the basic question, but we have seen some very strange behavior. The car has run with a stock chip in it, which I would assume would still have VATS. Why did it run with the stocker? The aftemarket chips we've tried all have VATS removed yet they won't run. We've taken live data and sometimes we get timing and injector pusles and sometimes not. In addition, the only time we can seem to get it to start at all is with timing retarded to extremes, like 40•.

Yet the computer is fine, we've swapped known good parts on it with no change. That's why I'm searching for some circuit that was removed in the conversion that the thing is looking for to fire.

bad chip?

Check to see if there's power from the ECM to the fuel pump relay with the key on.

With the original eprom VATS gets the signal to ground the starter enable relay.

With VATS removed the relay isn't grounded and the car won't start. Either enable VATS in the new tune or ground the relay permanently.

After I stranded a few times with VATS over the years, I thought it was a good idea to carry along an eprom with VATS removed. I too needed to short the relay to be able to start the engine with VATS removed.

The fuel pump runs. I can see voltage (and hear the pump run) at "key on". There is also a manual bypass that forces the pump to run. No luck in either state. Fuel in the rail is not in question, fuel to the cylinder may be.

We've tried several chips, two computers and two PROMs.

Does VATS disable the starter or the fuel pump? If so then this is not the problem, as both are powered and working. I should have mentioned that the car cranks just fine. Too easily, in fact. As if there is no load. Timing chain is intact.

Keep 'em coming!

When you say it won't start, is the starter engaging and the motor won't catch? Or the starter won't spin?

If the starter won't spin, you can bypass the starter enable relay in the dashboard by splicing the two wires together.

From vatssucks:

"Clip wire from Pin A ( DK GRN/WHT) and wire from Pin E (YEL) and wire them together. Leave some excess sticking out of the wiring harness in case you ever want to revert back to using the relay again."



If the motor will turn over, will it run with starting fluid? If so, it's a fuel delivery problem. Probably the ecm not providing fuel.

Have you put a noid light on the injectors to verify they are firing?

Also, are there any error codes that would indicated a bad ecm or chip?

Matthew

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Both, at least on LT1's.

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Yea, definatly should be checked.

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I was under the impression it disables 1) starter and 2) injector pulses via ECM, not the fuel pump itself. At least on the L98s, not sure on LT1s.

A simple question but often overlooked...did you check fuses?

The tune with VATS disabled takes care of the fuel part but not the starter.

Here comes a funny question: Is the dizzy mounted 180 degrees wrong?

The car cranks just fine, but won't fire. If VATS disables the injectors than this bears more investigation.

However, the car will not run on ether, either. Which leads me back to thinking fuel is not the issue. Dammit.

Distributer has been checked, it is in the proper position to #1 TDC.

Defective fuel injectors blocking each rail under load?

Try cranking it with only 6 injectors. Disconnect one on each side and play out the various possibilities.

Don't forget the 9th injector. That sucker can block the whole system as well.

Good idea, we'll try rotating injectors. The cold start injector has been eliminated from the system.

Thanks, updates later...

If it won't run on ether it's one of two issues - spark/timing or compression.

How long ago did it run with the stock chip? Recently? If so compression is probably good.

I'd check the spark with an adjustable spark checker - you can get one from lisle at the auto parts store for like $8. Check my old threads for a description. Then run through the FSM diagnostics for weak/no spark.

I saved this off a website but I don't remember from where. I wish I could give them credit. It's some quick and easy ignition testing:

Easy tests for HEI system:

1. Test for power at the pink BAT terminal. You should have battery voltage w/ the key in the start and RUN positions.

2. Connect the ground side of your test lamp to the battery POSITIVE cable. Probe the TACH terminal on the dist. cap while a helper attempts to start the engine. The test lamp should blink repeatedly as the engine cranks. No blink= bad module or pickup coil. Further testing is required to pinpoint the problem. Blink but no spark = bad ignition coil.

3. Remove the cap & rotor. Remove the green & white leads from the module. Connect your ohmmeter to the green & white leads. You should have approx. 800-1500 ohms depending on the ambient temperature. Open circuit (infinite ohms) = bad pickup coil.

Wiggle the green & white leads as you test. Ohm reading should remain constant if the leads are good. If the reading varies as the leads are wiggled, the pickup coil is bad. You'll often find broken pickup coil leads this way.

4. DVOM (meter) still connected to green & white leads. Set your DVOM to AC VOLTS. Have a helper crank the engine as you watch the AC VOLTS reading. A good pickup coil will produce about 3V AC when cranking. Less than approx. 2V AC indicates a bad pickup coil.

Here's the latest - research on the cam specs has revealed that it has an LSA of 106 and 38° of overlap. Not going to be easy to get an EFI car to run with that cam.

It's hard to have hope, but that's a pretty big issue.

New cam on the way.

Sounds to me like valves are hanging open. No compression.

Scratch that, I recall Mick feeling compression when checking #1 for tdc.

Here's a thought.

Stock chip (86 $32 mask) does not require reference pulses to fire injectors during cranking.

89 based chip ($6E mask) requires 8 reference pulses before firing injectors during crank for cleaner cold start emissions.

This can be edited in the bin.

;----------------------------------------------
; CRANK FUEL PW MULT Vs. REF PULSE LT 17
;
; 10-18-1997 Dissassemby of ARAP Lines= 16
;
; TBL = 256 * MULT
;---------------------------------------------
ORG $038B ; MULT DRP'S
;---------------------------------
LC38B FCB 0 ; 0.000 1
LC38C FCB 0 ; 0.000 2
LC38D FCB 0 ; 0.000 3
LC38E FCB 0 ; 0.000 4
LC38F FCB 0 ; 0.000 5
LC390 FCB 0 ; 0.000 6
LC391 FCB 0 ; 0.000 7
LC392 FCB 0 ; 0.000 8
LC393 FCB 128 ; 0.500 9
LC394 FCB 128 ; 0.500 10
LC395 FCB 64 ; 0.250 11
LC396 FCB 64 ; 0.250 12
LC397 FCB 64 ; 0.250 13
LC398 FCB 64 ; 0.250 14
LC399 FCB 64 ; 0.250 15
LC39A FCB 64 ; 0.250 16
;---------------------------------------------

I gotta figure something fishy with how the external ESC module is wired, that is preventing or interfering with the distributor reference pulses.