• Mustang Forums
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • Fox 5.0 Mustang Tech

91 5.0l cranks but no start, fuel pump keeps priming

  • Thread starter Thread starter Rhubyn
  • Start date Start date Jun 16, 2024
R

Rhubyn

New Member
Jun 15, 2024
1
0
1
Ontario
Jun 16, 2024
#1
  • Jun 16, 2024
  • #1
Hey y'all, I'm a little desperate and figured I'd try this forum as well. I have been trying to follow the checklist to the best of my abilities. I've got a 91 5.0l, it was running fine and I stored it over winter and now it won't fire back up. Cranks super healthy, fuel pump doesn't turn off, I can hear and feel fuel moving around in the injector lines. So far I've:

Replaced fuel pump, fuel filter, fuel pump relay, EEC relay, fuel pressure regulator, probably a couple of other things I'm forgetting.

I've got spark from ignition switch to coil, from coil to distributor, from distributor to spark plugs. I've definitely got air, I've re-set the distributor timing to TDC, I've brought my ecu to get tested and it tested out fine, all caps have been replaced in it. I get 12v at the ecu connector, I get 12v at coil, and 12v at ignition switch.

Tps sensor is sitting at a cool 0.86v, not 3.7+ or whatever it takes to think the engine is flooded from that. Pretty sure I'm getting 12v at stuff like MAF, I'm planning on checking everything again today, and if anyone wants exact module voltage please just ask.

Fusible link cable seems okay, I get like 4.5v to the injector red wires though. I read somewhere my multimeter might not be able to read the 12v pulse properly and it might show around 4.5v? Is that bs? Planning on cutting back the injector wiring harness and making sure nothing is broken. Was recommended to replace the TFI and sensor in the distributor but wondering if there was a way I could test that stuff without a noid light? Otherwise I think I'm gonna go buy a set today.

Any help or ideas would be greatly appreciated. She was running fine before I cannot for the life of me fix it and I've followed the checklist multiple times now haha
 

AeroCoupe

lube between the nut and the face. I know my lubes
Founding Member
Oct 28, 2001
5,911
4,032
183
Claremore, OK
Jun 16, 2024
#2
  • Jun 16, 2024
  • #2
Have you pulled codes?
 

Mcmahst

5 Year Member
Jan 19, 2021
686
270
83
Laguna Woods CA, fort Mohave AZ
Jun 16, 2024
#3
  • Jun 16, 2024
  • #3
Before I spent any more funds chasing the solution, after you pull the codes, you could test the TFI module before you replace it. Here is a quick link to a previous thread on that subject:

Any way to check if TFI module is bad?

89 5.0 with MSD Dist. wondering if is possible ti check if the module is bad? Going through the "crank but no start" check list.
stangnet.com
 

Trogdor

5 Year Member
Aug 30, 2018
195
119
53
Anna, TX
Jun 20, 2024
#4
  • Jun 20, 2024
  • #4
I had a similar issue where the fuel pump would constantly run with the key on and the engine would not start. Turned out to be time to replace the capacitors in the computer. I would take a look and see if it's time to send it in for repair.
 
Reactions: 4cylredfox89 and Mcmahst

Mustang5L5

That is…until I whipped out my Bissell
Mod Dude
Feb 18, 2001
43,260
17,945
224
Massachusetts
Jun 20, 2024
#5
  • Jun 20, 2024
  • #5
Fuel pump always running is a strong sign the ECU needs to be recapped
 
Reactions: 4cylredfox89 and Mcmahst

Mindseye007

10 years still blowing strong
5 Year Member
Oct 21, 2020
579
135
63
ontario
Jun 22, 2024
#6
  • Jun 22, 2024
  • #6
Rhubyn said:
Hey y'all, I'm a little desperate and figured I'd try this forum as well. I have been trying to follow the checklist to the best of my abilities. I've got a 91 5.0l, it was running fine and I stored it over winter and now it won't fire back up. Cranks super healthy, fuel pump doesn't turn off, I can hear and feel fuel moving around in the injector lines. So far I've:

Replaced fuel pump, fuel filter, fuel pump relay, EEC relay, fuel pressure regulator, probably a couple of other things I'm forgetting.

I've got spark from ignition switch to coil, from coil to distributor, from distributor to spark plugs. I've definitely got air, I've re-set the distributor timing to TDC, I've brought my ecu to get tested and it tested out fine, all caps have been replaced in it. I get 12v at the ecu connector, I get 12v at coil, and 12v at ignition switch.

Tps sensor is sitting at a cool 0.86v, not 3.7+ or whatever it takes to think the engine is flooded from that. Pretty sure I'm getting 12v at stuff like MAF, I'm planning on checking everything again today, and if anyone wants exact module voltage please just ask.

Fusible link cable seems okay, I get like 4.5v to the injector red wires though. I read somewhere my multimeter might not be able to read the 12v pulse properly and it might show around 4.5v? Is that bs? Planning on cutting back the injector wiring harness and making sure nothing is broken. Was recommended to replace the TFI and sensor in the distributor but wondering if there was a way I could test that stuff without a noid light? Otherwise I think I'm gonna go buy a set today.

Any help or ideas would be greatly appreciated. She was running fine before I cannot for the life of me fix it and I've followed the checklist multiple times now haha
Click to expand...
TFI Module 100% cooked , get a new one from Rockauto Motorcraft https://www.rockauto.com/en/moreinfo.php?pk=5434788&cc=1134010&pt=7172&jsn=17 or STANDARD MOTOR PRODUCTS LX223 https://www.rockauto.com/en/moreinfo.php?pk=49708&cc=1134010&pt=7172&jsn=932 and check your current TFI Module, by buying this off Ebay https://www.ebay.ca/itm/25553718100...pid=5335821607&customid=&toolid=10001&mkevt=1 don't for get to buy a 9 Volt Battery. and you can relocate your new TFI module with this https://www.mccullyracingmotors.com/ best one out there. and get some extra Arctic Silver 5 thermal paste https://www.ebay.ca/itm/16642480345...pid=5335821607&customid=&toolid=10001&mkevt=1 after its all installed your stang will fire right up.also if you ever need your ECU repaired this place is awesome and the best place to get it fixed at.

1986-2004 Ford Mustang A9L A9P ECU Repair Service

1986-2004 Ford Mustang A9L A9P ECU Repair Service Engine Computer Repair Please fill out the R&R form here once you've placed your order.ORInclude a note in the box with your order number and vehicle symptoms.A Trusted Product with LIFETIME WARRANTY QUICK TURN AROUND TIMEDomestic and...
www.theecuexchange.com
 

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor
Admin Dude
Jan 4, 1985
43,130
21,298
234
Box behind Walmart
Jun 23, 2024
#7
  • Jun 23, 2024
  • #7
Mindseye007 said:
TFI Module 100% cooked , get a new one from Rockauto Motorcraft https://www.rockauto.com/en/moreinfo.php?pk=5434788&cc=1134010&pt=7172&jsn=17 or STANDARD MOTOR PRODUCTS LX223 https://www.rockauto.com/en/moreinfo.php?pk=49708&cc=1134010&pt=7172&jsn=932 and check your current TFI Module, by buying this off Ebay https://www.ebay.ca/itm/25553718100...pid=5335821607&customid=&toolid=10001&mkevt=1 don't for get to buy a 9 Volt Battery. and you can relocate your new TFI module with this https://www.mccullyracingmotors.com/ best one out there. and get some extra Arctic Silver 5 thermal paste https://www.ebay.ca/itm/16642480345...pid=5335821607&customid=&toolid=10001&mkevt=1 after its all installed your stang will fire right up.also if you ever need your ECU repaired this place is awesome and the best place to get it fixed at.

1986-2004 Ford Mustang A9L A9P ECU Repair Service

1986-2004 Ford Mustang A9L A9P ECU Repair Service Engine Computer Repair Please fill out the R&R form here once you've placed your order.ORInclude a note in the box with your order number and vehicle symptoms.A Trusted Product with LIFETIME WARRANTY QUICK TURN AROUND TIMEDomestic and...
www.theecuexchange.com
Click to expand...
What did you do
 
Reactions: Mcmahst and Mindseye007

4cylredfox89

Member
Dec 2, 2021
20
4
13
California
Jul 29, 2024
#8
  • Jul 29, 2024
  • #8
OP did you ever solve your issue?
 
You must log in or register to reply here.

Similar threads

A
1987 5.0 speed density Foxbody crank no start
  • Alan2204
  • May 23, 2026
  • Fox 5.0 Mustang Tech
Replies
10
Views
313
Fox 5.0 Mustang Tech May 30, 2026
Mcmahst
B
Electrical Why does my fox body keep frying eecs
  • brandyn200
  • Jun 20, 2026
  • Fox 5.0 Mustang Tech
Replies
8
Views
270
Fox 5.0 Mustang Tech Jun 25, 2026
AeroCoupe
Resolved 93 Mustang 5.0 - Cranks but does not start
  • dan50
  • Jul 18, 2026
  • Fox 5.0 Mustang Tech
Replies
6
Views
141
Fox 5.0 Mustang Tech Jul 18, 2026
dan50
8
Electrical Crank-no start ... no spark ... no injector pulse, was it something I did? (redux)
  • 85gtCOBRA
  • Oct 28, 2025
  • Fox 5.0 Mustang Tech
Replies
2
Views
573
Fox 5.0 Mustang Tech Oct 29, 2025
85gtCOBRA
8
F
2004 Mustang GT – Fuel Pump Not Priming
  • Fayio
  • Apr 22, 2026
  • SN95 4.6L Mustang Tech
Replies
7
Views
310
SN95 4.6L Mustang Tech Apr 27, 2026
n0v8or
N
Share:
Bluesky Email Share Link
  • Mustang Forums
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • Fox 5.0 Mustang Tech
Menu
Log in

Register

  • Forums
  • What's new
  • Media
  • Resources
  • Contact
  • Sponsor
X

Privacy & Transparency

We use cookies and similar technologies for the following purposes:

  • Personalized ads and content
  • Content measurement and audience insights

Do you accept cookies and these technologies?

X

Privacy & Transparency

We use cookies and similar technologies for the following purposes:

  • Personalized ads and content
  • Content measurement and audience insights

Do you accept cookies and these technologies?