Electrical Stumped No Start...

S

sydhawk

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Aug 10, 2001

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Oct 28, 2025

#1

• Oct 28, 2025

• #1

Here's the deal. 86 5.0 that's been converted to mass air that will not start. It has a PMS for tuning and the weird thing is, if you just touch the throttle it immediately shows WOT on the PMS. I've checked everything. TFI, PIP, TPS, Plugs and so on. TPS reads exactly as it should at the sensor and all the way right down at the EEC. Obviously the WOT is why the car won't open the injectors to start. Even tried a different EEC, shows the same thing. Tried without the PMS hooked up, same deal. All fusable links have been checked, no broken or pinched wires. It's baffling. Why is it going to WOT even though the TPS works exactly like it should voltage wise. All grounds are good as well.
I've also followed the crank no start thread and tried those suggestions. Redid the injector harness and check the salt and pepper shakers too.
Any help would be appreciated.

 

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

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#2

• Oct 28, 2025

• #2

Did the car ever run with this harness installed and a MAF EEC?

What I'm asking about is whether the mass air conversion wiring has ever been tested and verified?


What are your other mods?

 

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S

sydhawk

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Oct 28, 2025

#3

• Oct 28, 2025

• #3

Yup car ran fine with the MAF conversion. H/C/I, blower. 36lb with matching meter, tuned with a PMS. Only thing I noticed that was off was when checking ohms from injector terminal to injector body, there is nothing. When doing injector terminal to terminal, the resistance is fine. Car sat for a few years and now won't start.

 

Last edited: Oct 28, 2025

General karthief

wonder how much it would cost to ship you a pair

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#4

• Oct 28, 2025

• #4

Will the computer talk to ya??
Will it start with starting fluid?

 

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S

sydhawk

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#5

• Oct 28, 2025

• #5

No codes. Computer works fine in another car. Didn't try starter fluid because the injectors don't open. Noid test/no clicking when trying to start. Noid test suggested a short, took the injector harness out, went over every mm of it and redid everything. Checked all the harness wires back to the puter, nothing wrong. Everything works as it should. I've even checked the TPS voltage on the board in the puter.
My issue is trying to find out why the computer thinks it's in WOT/flood mode and shutting the injectors down during start up and why when I move the throttle maybe 1mm with KOEO the PMS reads the TPS signal as WOT. Car has plenty of spark, fuel.

 

rednotch

I'd like to remain having one chocolate starfish

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#6

• Oct 28, 2025

• #6

Unplug the tps and see if it fires, then see if it fires off starting fluid if it doesn't.. Either tps or the pms is messed up or voltage readings are off if tps shows correct voltage up except for on the pms unit. Are you hearing the fuel pump prime at all when you turn they key and seeing pressure at the rails?

 

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AeroCoupe

lube between the nut and the face. I know my lubes

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#7

• Oct 29, 2025

• #7

Have you back probed the TPS and confirmed that at idle it’s providing a voltage to the ECU in the range of 0.6 to 1.1 volts? The allowable range is actually 0.5 to 1.25 volts but keeping it just above and just below the min/max allows for variations.

 

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S

sydhawk

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Oct 29, 2025

#8

• Oct 29, 2025

• #8

AeroCoupe said:

Have you back probed the TPS and confirmed that at idle it’s providing a voltage to the ECU in the range of 0.6 to 1.1 volts? The allowable range is actually 0.5 to 1.25 volts but keeping it just above and just below the min/max allows for variations.

Click to expand...

Yes....I've even checked the voltage at the ECU. Everything is within range.... 0.92 at idle, 4.64 at WOT...nice and smooth curve from idle to WOT.

 

Last edited: Oct 29, 2025

S

sydhawk

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Oct 29, 2025

#9

• Oct 29, 2025

• #9

rednotch said:

Unplug the tps and see if it fires, then see if it fires off starting fluid if it doesn't.. Either tps or the pms is messed up or voltage readings are off if tps shows correct voltage up except for on the pms unit. Are you hearing the fuel pump prime at all when you turn they key and seeing pressure at the rails?

Click to expand...

The PMS is showing what the issue is but is not the problem. Everything is the exact same without it being hooked up. Plenty of fuel and pressure at the rails. Plenty of spark. TPS reads perfect at the sensor and the ECU. Noid test suggest a short going to injectors....re-did the injector harness/salt and pepper, checked all ground and have traced it all the way to the ECU. All readings for resistance, voltage are normal. ECU works fine in another car yet for some reason the injectors aren't firing.