EFI No Start After Sitting - Ron Francis Harness Mustang 5.0

[SelectiveSlug]

Hello EB Community! I'm hoping the EFI experts can help me out as I'm struggling to diagnose my Bronco.

Bronco Details:
1989 Mustang 5.0 Ron Francis harness, factory computer. C4 Auto. This setup was installed roughly 10 years ago and it used to run perfect. About 5 years ago I decided to park the bronco and redo the suspension (was supposed to be a winter project, yikes). I finally finished the suspension, started the bronco up and drove it to my new garage. It then sat for about another 9 months. I went to go start it and it will not fire up. I have spark and it cranks just fine.

Fuel System Details:
One low pressure fuel pump mounted near a stock tank and an in line filter. Quart size spin on filter mounted on the firewall and then a high pressure pump on the inner fender. AN Lines after the high pressure pump and a return line. Factory ford stock size injectors new when installed 10 years ago.

New parts purchased in the last 2 months:
Fuel tank, sending unit
high pressure pump - reads about 38 psi
sent the computer to be rebuilt
Fuel pump relay
idle air bypass

Noteworthy:
I have power at the injectors but the are not pulsing when cranking.
When I pull the ECM relay the fuel pump runs, when I put it back in it stops and I lose power to the relay.
I found the self test portion of the harness but I cannot figure out what to do with it. Is there a way to plug in a OBD scanner to it? The harness instructions mentioned:"Locate the V.I.P self test connectors and connect a jumper wire between the grey wire (VIP->CTS SPL) located in the large VIP connector and the tan wire (ECM 48->VIP) located in the single connector" - I am not sure what they mean by connect a jumper between the wires, does this trigger the check engine light to flash the code?

It feels like the computer is bad even though it was just rebuilt. Or the only other noteworthy thing I can think of is since it sat for a while, the rubber inside the AN lines may have come apart (when I first started it I had to replace the line directly after the high pressure bump as it was leaking) and may have clogged the injectors?? But then again they aren't plusing so I think its more of an electrical issue. I didn't touch the harness or grounds but it could also be possible a rodent got to it. Everything appears to be fine visually.

I appreciate any extra insight!

 

[Timmy390]

Check for spark. Injectors will not fire if you have no PIP (Hall sensor or pickup coil) inside the distributor. Get TFI tested.

I had this issue when building my EFI. The distributor went bad while sitting on my work bench. Worked when pulled. Odd things happen

Tim

 

[DirtDonk]

Fuel pumps don't like to sit either. Especially when they are almost new, and have gas in them when put to bed.
And that 38psi is a bit on the low side, but would not be enough to keep it from running I would not think. Could even be just a variation in the pressure gauge giving you a low reading.
Should be 42-45 psi I think? Man, it's been a long time since I quoted pressure numbers! So take it with a grain of sand and wait for someone with a fresh memory to chime in.

Was going to mention the PIP as well. First thing I thought of, but you say you have spark?
How is the spark and how did you test? Did you use a timing light on each wire, or pull a wire and check spark out the end?
Either way, was it a good healthy white/blue spark, and consistent when cranking? Or was it anything other than that?

Paul

 

[73azbronco]

Insufficient fuel pressure

 

[SelectiveSlug]

Check for spark. Injectors will not fire if you have no PIP (Hall sensor or pickup coil) inside the distributor. Get TFI tested.

I had this issue when building my EFI. The distributor went bad while sitting on my work bench. Worked when pulled. Odd things happen

Tim

I'll have to revisit how to test the PIP - I kind of figured since i had spark it wasn't the issue. Can anyone confirm if that isn't the case?

Fuel pumps don't like to sit either. Especially when they are almost new, and have gas in them when put to bed.
And that 38psi is a bit on the low side, but would not be enough to keep it from running I would not think. Could even be just a variation in the pressure gauge giving you a low reading.
Should be 42-45 psi I think? Man, it's been a long time since I quoted pressure numbers! So take it with a grain of sand and wait for someone with a fresh memory to chime in.

Was going to mention the PIP as well. First thing I thought of, but you say you have spark?
How is the spark and how did you test? Did you use a timing light on each wire, or pull a wire and check spark out the end?
Either way, was it a good healthy white/blue spark, and consistent when cranking? Or was it anything other than that?

Paul

I just replaced the high pressure pump yesterday so I'm not too worried about fuel pressure (I think it was more like 38-40 psi range, is that enough)? I put an in-line spark tester on the plug wire to the front left cylinder and it lit up and seemed pretty strong.

Insufficient fuel pressure

Would that prevent the injectors from pulsing? What should the PSI be?

Thanks all!

 

[bax]

Quick test. Dump some gas down the intake. Try and start it. It may run once the computer sees a higher rpm. just do it.

 

[4x4man514]

Hello EB Community! I'm hoping the EFI experts can help me out as I'm struggling to diagnose my Bronco.

Bronco Details:
1989 Mustang 5.0 Ron Francis harness, factory computer. C4 Auto. This setup was installed roughly 10 years ago and it used to run perfect. About 5 years ago I decided to park the bronco and redo the suspension (was supposed to be a winter project, yikes). I finally finished the suspension, started the bronco up and drove it to my new garage. It then sat for about another 9 months. I went to go start it and it will not fire up. I have spark and it cranks just fine.

Fuel System Details:
One low pressure fuel pump mounted near a stock tank and an in line filter. Quart size spin on filter mounted on the firewall and then a high pressure pump on the inner fender. AN Lines after the high pressure pump and a return line. Factory ford stock size injectors new when installed 10 years ago.

New parts purchased in the last 2 months:
Fuel tank, sending unit
high pressure pump - reads about 38 psi
sent the computer to be rebuilt
Fuel pump relay
idle air bypass

Noteworthy:
I have power at the injectors but the are not pulsing when cranking.
When I pull the ECM relay the fuel pump runs, when I put it back in it stops and I lose power to the relay.
I found the self test portion of the harness but I cannot figure out what to do with it. Is there a way to plug in a OBD scanner to it? The harness instructions mentioned:"Locate the V.I.P self test connectors and connect a jumper wire between the grey wire (VIP->CTS SPL) located in the large VIP connector and the tan wire (ECM 48->VIP) located in the single connector" - I am not sure what they mean by connect a jumper between the wires, does this trigger the check engine light to flash the code?

It feels like the computer is bad even though it was just rebuilt. Or the only other noteworthy thing I can think of is since it sat for a while, the rubber inside the AN lines may have come apart (when I first started it I had to replace the line directly after the high pressure bump as it was leaking) and may have clogged the injectors?? But then again they aren't plusing so I think its more of an electrical issue. I didn't touch the harness or grounds but it could also be possible a rodent got to it. Everything appears to be fine visually.

I appreciate any extra insight!

dealing with the same problems.

if you look at the harness instructions there is a little picture at the botom of the page showing which wires to jump. a simple piece of wire with a spade connector on both ends. plug into the vip wire and the separate brown wire plug. then when you turn the key on the check engine light(assuming you have one) will flash codes at you. hope this helps.

im thinking mine at 38# is insufficient pressure as well but i havent had a chance to check yet.

good luck!

 

[Viperwolf1]

38 psi is fine. It should run with that.

 

[4x4man514]

38 psi is fine. It should run with that.

well that puts me back at no clue what my problem is

 

[Viperwolf1]

well that puts me back at no clue what my problem is

Try Bax's suggestion above. If it runs you have fuel delivery issues. If it doesn't run you have ignition or timing or compression problems.

 

[SelectiveSlug]

Try Bax's suggestion above. If it runs you have fuel delivery issues. If it doesn't run you have ignition or timing or compression problems.

Dumb question but I have the factory intake on it, how should I go about dumping fuel into the intake?

Also, if I have spark but the pip isn’t telling the injectors to operate I’m worried the distributor will be making it look like there is a fuel problem, right?

 

[Viperwolf1]

Take the hose or filter off the throttle body and squirt some fuel behind the butterfly.

 

[SelectiveSlug]

Take the hose or filter off the throttle body and squirt some fuel behind the butterfly.

Ah that makes sense. I’ll try that after work tomorrow.

 

[Timmy390]

Also, if I have spark but the pip isn’t telling the injectors to operate I’m worried the distributor will be making it look like there is a fuel problem, right?

TFI module could be switching the coil primary circuit equaling spark but not creating a PIP signal. Local parts stores can test the TFI

Tim

 

[73azbronco]

starter fluid usually has a nozzle, you can spray it down intake.

 

[4x4man514]

TFI module could be switching the coil primary circuit equaling spark but not creating a PIP signal. Local parts stores can test the TFI

Tim

Good to know. Ill have to get mine checked

 

[SelectiveSlug]

Ok - I was able to take the intake piping off and get it to run for 3-4 seconds on the starter fluid. At this point I've replaced everything on the fuel system except the injectors. The fuel pump relay isn't getting power from the computer so I'm leaning towards PIP signal. It seems counter intuitive to think the sensor on the distributor would be telling the fuel system not to run but that seems possible, right?

 

[73azbronco]

things that will prevent injectors from firing, crank position sensor, which is basically your distributor, unless you have full on explorer motor.

 

[Viperwolf1]

Ok - I was able to take the intake piping off and get it to run for 3-4 seconds on the starter fluid. At this point I've replaced everything on the fuel system except the injectors. The fuel pump relay isn't getting power from the computer so I'm leaning towards PIP signal. It seems counter intuitive to think the sensor on the distributor would be telling the fuel system not to run but that seems possible, right?

Does the pump run for 2 seconds when you turn the key on? It doesn't need a pip to do that.

 

[SelectiveSlug]

Does the pump run for 2 seconds when you turn the key on? It doesn't need a pip to do that.

It does. I’m getting fuel to the high pressure pump and I can hear them run for 2 seconds