[92MustangGT5.0L]

I have a 1992 Mustang Gt 5.0 and I’m having a problem with it shutting off when it’s running. The problem started a long time ago and was extremely random and it would just shut off for maybe 1-5 seconds and then the engine would automatically turn back on (I assume because I was driving down the road and since it’s a 5-speed, it fired back up because of the wheels turning the motor). However, the problem is getting a lot worse and a lot more frequent.

I put a scanner on it and read the codes and it came up with 3 codes: 34, 67, & 96.
34 = Insufficient EGR flow or EVP voltage hight (SONIC) or PFE sensor voltage high or out of specification.
67 = Clutch switch circuit failure / neutral drive switch (NDS) circuit failure, circuit open; or A/C input high.
96 = Fuel pump secondary circuit fault / high speed fuel pump relay open.

After doing some research on this problem, it seems that the problem might be the fuel pump relay. I wasn’t sure where the relay was located, but what I was told is that it’s either under the driver’s seat or on the passenger side fender well in front of the shock tower. Upon inspecting my car, I found two relays on the passenger side fender well in the front of the shock tower. From what I was told, one relay is for the A/C cutoff at WOT and the other is the fuel pump relay.

So I went to NAPA and bought a new fuel pump relay. When I got home and went to install it, I discovered the shape, size and pins weren’t the same as the one on my car (SEE PICTURES). All the research I’ve done shows the fuel pump relay is the same as the one I bought from Napa (on the right in the pictures). But as you can see, mine is a different size and shape and has more of a standard relay pin layout.

Is the relay I found on my car the fuel pump relay or is it something else? If it’s not, where is it located? If this is the fuel pump relay, why is it different than the one from Napa and all the other auto part stores I’ve looked at? Autozone has the same relay as Napa, which is different than mine. Not sure what to do at this point. I don’t know what relay I have or what to buy to replace it. Can anyone shed some light on this? Thanks.

 

[92MustangGT5.0L]

Let me add something to this scenario that I just remembered. There was one incident when I was driving down the highway and I had the radio on and all of a sudden the radio shut off for about 3-5 seconds and then came back on (car still running). Then about 30 seconds later, the car shut off and came back on. So if the radio is shutting off, but the car is still running that tells me that the fuel pump relay isn?t the issue??? Is that correct?

Given the trouble codes that showed up (that I posted in my original post), what do you guys thing is causing my problem with the car shutting off? Is this more of an ignition switch issue?

 

[wbrockstar]

The fuel pump relay is located on the front side of the passenger strut tower,near the maf sensor,on late 92 & all 93 Mustangs.If youre Mustang is an early 92 model,the fp relay will be located under the driver seat.*CLUE*- if your car has 2 relays near the maf sensor,instead of 1,youve got the later 92 model.There are two relays there on a late 92 model,the fuel pump relay & the ac wot cutoff relay.If youve got the later 92
model with 2 relays,the relay you need is part # LMS-14089A.
If youve got an early 92 model,with the fp relay under the seat,the first link below is the relay you need.
If youve got the later 92-93 model,with the fp relay at the passenger strut tower,use the second link below.
https://lmr.com/item/DY864/1986-1992-Mustang-Fuel-Pump-Relay

https://lmr.com/item/LRS-14089A/1993-Mustang-Fuel-Pump-Relay


However your problem does sound like more of an ignition switch issue,since a bad fuel pump relay will only affect the fuel pump itself,nothing else.The ignition switch usually begins separating between its metal & plastic section.The link below details its installation. Another thing to check,that'll cause your problem,is a loose,corroded or defective starter solenoid.It grounds by making clean/tight contact between its rear panel & the fender apron,so make sure those surfaces are sanded clean and the mounting bolts are tight.Everything you see,in the wiring diagram below, attached to the battery+ stud on the solenoid gets its "always hot" power supply from the solenoid,so its a very critical component.

If code 67 is a valid error code,instead of operator error,it can also cause the engine to stall,but its mainly when slowing down to come to a stop.Operator error means you left the transmission in gear,instead of neutral, when running codes or you left the ac on during the test.
NSS/Clutch Pedal Switch Code 67 Troubleshooting

Replace a 1979-1993 Ignition Switch Assembly

 

[92MustangGT5.0L]

The fuel pump relay is located on the front side of the passenger strut tower,near the maf sensor,on late 92 & all 93 Mustangs.If youre Mustang is an early 92 model,the fp relay will be located under the driver seat.*CLUE*- if your car has 2 relays near the maf sensor,instead of 1,youve got the later 92 model.There are two relays there on a late 92 model,the fuel pump relay & the ac wot cutoff relay.If youve got the later 92
model with 2 relays,the relay you need is part # LMS-14089A.
If youve got an early 92 model,with the fp relay under the seat,the first link below is the relay you need.
If youve got the later 92-93 model,with the fp relay at the passenger strut tower,use the second link below.
https://lmr.com/item/DY864/1986-1992-Mustang-Fuel-Pump-Relay

https://lmr.com/item/LRS-14089A/1993-Mustang-Fuel-Pump-Relay


However your problem does sound like more of an ignition switch issue,since a bad fuel pump relay will only affect the fuel pump itself,nothing else.The ignition switch usually begins separating between its metal & plastic section.The link below details its installation. Another thing to check,that'll cause your problem,is a loose,corroded or defective starter solenoid.It grounds by making clean/tight contact between its rear panel & the fender apron,so make sure those surfaces are sanded clean and the mounting bolts are tight.Everything you see,in the wiring diagram below, attached to the battery+ stud on the solenoid gets its "always hot" power supply from the solenoid,so its a very critical component.

If code 67 is a valid error code,instead of operator error,it can also cause the engine to stall,but its mainly when slowing down to come to a stop.Operator error means you left the transmission in gear,instead of neutral, when running codes or you left the ac on during the test.
NSS/Clutch Pedal Switch Code 67 Troubleshooting

Replace a 1979-1993 Ignition Switch Assembly

Thank you for that info and providing links and part numbers! That helps a lot. I'm definitely going to be using diagram to do some testing. Regarding the code 67, it very well could have been my fault. I didn't realize when I pulled the codes that I should have had the tranny in neutral. So I'll pull the codes again and see if it's still there. I know for a fact the A/C wasn't on. And thankfully if I end up having to change the ignition switch, they're only $14 at Autozone. Thanks again for the info. It's very much appreciated!!!

 

[92MustangGT5.0L]

Wbrockstar, thanks for that info and the links you provided. According to your info, I definitely have a late 92, as I have the two relays by the shock tower and I have located the fuel pump relay. Unfortunately, it doesn't match the ones the autopart stores have in their computer system. But what I did notice about the factory plug I have is it has the common pin layout of a majority of the generic relays I've seen in the autoparts stores. I guess what I'm saying is I assume I can pick up one of these generic or common style relays and use it in place of my factory fuel pump relay???? I guess the only other thing I would need to know is what amperage relay do I need to get? What is the amperage rating of the factory relay?

I bought one of these generic fuel pump relays to power a low pressure electric fuel pump for the rear gas tank that I used to fill the front gas tank on my 78 F150 that I had installed EFI on and it seems to work just fine and it's more than half of the cost of the factory Mustang relay. https://www.summitracing.com/search?SortBy=BestKeywordMatch&SortOrder=Ascending&keyword=SUM-890023. So do you think I could use this relay in place of the factory Mustang relay?

Another guy had also mentioned that the ignition switch on these Mustangs have had issues and are common problem. At one time they had a recall on them. I'm thinking I might just replace the ignition switch as a preventative safety measure whether it needs replaced or not. Who knows, I might get lucky and it resolves my problem with the car shutting off.

I'll definitely look into the starter solenoid issue you mentioned just to rule that out as a possible problem.

Regarding the 67 error code....I didn't realize I had to have the tranny in neutral in order to read the codes. So that 67 code could have been my fault because I think I had the tranny in gear when I pulled the codes. I'll pull the codes again and this time I'll have the tranny in neutral. Thanks for that information. I guess you're never too old to learn something new....LOL

 

[wbrockstar]

Wbrockstar, thanks for that info and the links you provided. According to your info, I definitely have a late 92, as I have the two relays by the shock tower and I have located the fuel pump relay. Unfortunately, it doesn't match the ones the autopart stores have in their computer system. But what I did notice about the factory plug I have is it has the common pin layout of a majority of the generic relays I've seen in the autoparts stores. I guess what I'm saying is I assume I can pick up one of these generic or common style relays and use it in place of my factory fuel pump relay???? I guess the only other thing I would need to know is what amperage relay do I need to get? What is the amperage rating of the factory relay?

I bought one of these generic fuel pump relays to power a low pressure electric fuel pump for the rear gas tank that I used to fill the front gas tank on my 78 F150 that I had installed EFI on and it seems to work just fine and it's more than half of the cost of the factory Mustang relay. https://www.summitracing.com/search?SortBy=BestKeywordMatch&SortOrder=Ascending&keyword=SUM-890023. So do you think I could use this relay in place of the factory Mustang relay?

Another guy had also mentioned that the ignition switch on these Mustangs have had issues and are common problem. At one time they had a recall on them. I'm thinking I might just replace the ignition switch as a preventative safety measure whether it needs replaced or not. Who knows, I might get lucky and it resolves my problem with the car shutting off.

I'll definitely look into the starter solenoid issue you mentioned just to rule that out as a possible problem.

Regarding the 67 error code....I didn't realize I had to have the tranny in neutral in order to read the codes. So that 67 code could have been my fault because I think I had the tranny in gear when I pulled the codes. I'll pull the codes again and this time I'll have the tranny in neutral. Thanks for that information. I guess you're never too old to learn something new....LOL

If Im not mistaken,the part #'s on the ac wot cutoff & fuel pump relay are the same.Just remove the ac wot relay & plug it into the fuel pump relay wiring harness to see if it fixes the issue.The ac wot cutoff relay cuts power to the ac compressor when you go wot,so the engine wont lose power from the parasitic drag of the compressor.If you swap relays & the problem disappears,you can either leave the ac relay plugged into the fp relay harness (to prevent you from spending cash on a new relay) or buy a new relay with the same pin layout,voltage,etc.The ac relay will have to be replaced later when the weather warms up & you want ac.

Yeah the ignition switch is very well known for causing problems.Its a good idea to replace the ignition switch harness pigtail too,since shorting in the switch will cause the wire insulation & plastic to melt or age will cause the insulation to become brittle.

I'll have to research the relay amperage.

I saw the identical thread you posted @ Stangnet & it looks like Jrichker answered all of the other questions you had related to the other codes you had,etc.So he gave great testing advice for your issues.
Theres usually one or two guru's on every Mustang forum that will always have the right answers & list testing procedures needed to pinpoint the issues youre having.
Jrichker is the man @ Stangnet.
Joel 5.0 is the man @ SBF TECH
NX Coupe is the man @ Modded Mustangs
TMoss is the man @ EEC Tuning.org

 

[92MustangGT5.0L]

If Im not mistaken,the part #'s on the ac wot cutoff & fuel pump relay are the same.Just remove the ac wot relay & plug it into the fuel pump relay wiring harness to see if it fixes the issue.The ac wot cutoff relay cuts power to the ac compressor when you go wot,so the engine wont lose power from the parasitic drag of the compressor.If you swap relays & the problem disappears,you can either leave the ac relay plugged into the fp relay harness (to prevent you from spending cash on a new relay) or buy a new relay with the same pin layout,voltage,etc.The ac relay will have to be replaced later when the weather warms up & you want ac.

Yeah the ignition switch is very well known for causing problems.Its a good idea to replace the ignition switch harness pigtail too,since shorting in the switch will cause the wire insulation & plastic to melt or age will cause the insulation to become brittle.

I'll have to research the relay amperage.

I saw the identical thread you posted @ Stangnet & it looks like Jrichker answered all of the other questions you had related to the other codes you had,etc.So he gave great testing advice for your issues.
Theres usually one or two guru's on every Mustang forum that will always have the right answers & list testing procedures needed to pinpoint the issues youre having.
Jrichker is the man @ Stangnet.
Joel 5.0 is the man @ SBF TECH
NX Coupe is the man @ Modded Mustangs
TMoss is the man @ EEC Tuning.org

Yeah, I used the shotgun strategy and posted this question on 3 different forums. I figured someone would know the answer to my questions. I was really impressed by Jrichker's response. That guy knows his ****!! I'm going to use his diagrams to troubleshoot my relay issue. But I'm going to just replace the ignition switch just because it is known to have problems and it's 25 years old. I figure $14 is cheap insurance and peace of mind. It's not hard to change so I'll tackle that project after work sometime this week. And you're right about the pigtail, so I'll probably change that also.

Thanks for the info on which guys to contact on which site. That will help a lot. I'm on this site, Stangnet, Corral.net, & Modded Mustangs. But I'm not on any of them that much, just when I need some help. I have used Stangnet & Corral.net the most. I might have to join SBF Tech & EEC Tuning also. When it comes to fuel injection tuning and stuff like that, I'll need all the help I can get.

 

[wbrockstar]

Yeah, I used the shotgun strategy and posted this question on 3 different forums. I figured someone would know the answer to my questions. I was really impressed by Jrichker's response. That guy knows his ****!! I'm going to use his diagrams to troubleshoot my relay issue. But I'm going to just replace the ignition switch just because it is known to have problems and it's 25 years old. I figure $14 is cheap insurance and peace of mind. It's not hard to change so I'll tackle that project after work sometime this week. And you're right about the pigtail, so I'll probably change that also.

Thanks for the info on which guys to contact on which site. That will help a lot. I'm on this site, Stangnet, Corral.net, & Modded Mustangs. But I'm not on any of them that much, just when I need some help. I have used Stangnet & Corral.net the most. I might have to join SBF Tech & EEC Tuning also. When it comes to fuel injection tuning and stuff like that, I'll need all the help I can get.

Yeah I agree,Jrichker definitely knows his **** &
Joel 5.0 is even better.Jrichker is currently employed in the computer field & Joel was formerly employed in the computer manufacturing/testing field,so when you combine their computer knowledge with their automotive knowledge,it makes them guru's in the efi world,especially the Foxbody world.

 

[92MustangGT5.0L]

Well, I do believe I found out why my Mustang has been shutting off. I bought a new ignition switch and now I need to buy a new connector. I'm thankful this isn't a very expensive or difficult fix. I'm even more thankful that I caught it before my car went up in flames.

 

[wbrockstar]

Boy that was close.Luckily you had the radio shutting off alongside the engine stalling symptoms,otherwise you might not have bothered checking the ignition switch.
You caught it just in time.Good job

 

[raudermaster]

Not to hijack or anything, but when your car would shut off, would it crank back up right away? I'm having a similar issue where it will die once in a while, but it won't crank at all and I have to wait a little, but I have all my lights etc. Then it randomly will let me start it back up, mine's an auto though. I'm hoping it might be something stupid like yours with the ignition switch.

 

[wbrockstar]

@ raudermaster

When you say it wont crank at all,do you mean??
1) the starter wont turn over
2) the starter turns over but the engine wont start & run

If its #1,follow the test steps in the link below.
https://www.stangnet.com/mustang-forums/threads/bypass-clutch-safety-switch.771363/

If its #2,does the problem mainly occur after the engine has warmed up?? If yes,that usually indicates the pip sensor (inside the distributer) tfi module or fuel pressure regulator is to blame.When the no start condition occurs,remove the spout plug thats part of the tfi module harness then try to restart it.If it starts,that indicates the pip sensor is bad.The tfi module can be tested at Autozone,but youll have to buy a tfi socket to remove it from the distributer.Make sure they run it through numerous cycles so it'll get hot.A defective fuel pressure regulator will also cause a hot no start.Let the engine idle at operating temp,remove the vacuum hose from the regulator and check the inside of it for wet fuel.Check the regulator vacuum port too,for seeping fuel.If either condition is present,the regulator is bad.
Dont buy generic components at the local parts store.They will go out anywhere from 3 months to a few days.Oem Ford Motorcraft parts can be sourced at RockAuto for far less than a dealer.