Miata 5.0-HO SEFI (1987) no start fuel injection problem

BMWKolb

Member
Jan 27, 2021
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Sahuarita, AZ 85629, USA
engine picture 2.JPG
I have installed a rebuilt 1987 Mustang 5.0-HO engine into my 2003 Miata.
Ran OK for around 50 miles as I was troubleshooting various problems.
Engine quit on my way home from hardware store. Friend had to tow me rest of the way home.
Engine cranks but will not start or even try to start.
1. Ignition system checked with spark tester and is good. Changed out coil and TFI anyway.
2. Fuel supply pressure measured at 39 psi. Good
3. Spark plugs dry, no fuel. Pulled cylinder #5 fuel injector connector. 12V power on red wire. Tested black wire with test light ground lead connected to power. Result was light does not come on during cranking. Checked continuity of black wire to ECM pin #14 wire and was good. Harness good.
4. Tried 3 different ECM's and no change.
5. All ground wires checked and are good. Including ECM ground. Pulled distributor spout and no impact. Cranks but will not start.
Any suggestions????
I am a pretty good mechanic but this problem has me stumped!
Tim
Tucson, AZ
 
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7991LXnSHO

wanna catch the space herp
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Noobz, isn’t this a rebodied 5.0?

Kolb, the tech info diagnostics you will need are under the 5.0 tech sticky threads. The good news is if it ran, you are more likely to be able to get through the diagnostic procedures than if it never did.
 

Mustang5L5

Put lubricant all over the balls
Mod Dude
Feb 18, 2001
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Feel like this would get better response in the 5.0 tech board...no?

Can someone link the 5.0 crank, no start checklist?

Edit: post 3

 

BMWKolb

Member
Jan 27, 2021
3
3
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66
Sahuarita, AZ 85629, USA
Update
Connected OBD1 Code Reader and conducted Key On Engine Off with cold engine.
Codes with new (reconditioned) ECM
67 - clutch switch open circuit (not connected to ecm, just miata starter circuit which work correctly)
87 Fuel pump circuit fault (fuel pump connected on Miata system with continuous on when key on)
10 - separation code
11 Pass Code (OK)

Does this self test check the injectors?
 

Mustang5L5

Put lubricant all over the balls
Mod Dude
Feb 18, 2001
36,522
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Massachusetts
Does this self test check the injectors?

No. System is not smart enough to do that. You'll need to employ more old-school troubleshooting techniques. With the fuel rail pressurized, touch the injectors with a 9V battery and leads. They should click and you'll see the fuel pressure drop. ALso, if you set a DMM to resistance, you should get 14.4 ohms on each injector.

Do you have spark? The PIP in the distributor tends to crap out, leaving you with a no spark situation. Pull a spark plug and ground it on the motor and crank and see if you have spark (or use a proper spark tester)

Also FYI, depressing the throttle to the floorboard during crank will max out the TPS voltage and put the ECU in flood clear. The injectors won't fire. Helps clear out a bunch of fuel you might dump in the cylinders while testing injectors
 
Last edited:

a91what

SendMeUrDataLog
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you can also test the injector outputs with a noid light tester.
the above is an affordable example if you do not own one. This is very handy to have around when you are doing any troubleshooting
 
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