Engine cranks, but does not start

Tiny
WAYNE69
  • MEMBER
  • 2005 JEEP GRAND CHEROKEE
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 12,000 MILES
Please bear with me, it's a long one. In November my vehicle started not starting. I couldn't hear the fuel pump. I replaced the relay and fuse. I started fine for a few weeks. I noticed that the battery was draining and I had the alternator tested. It was bad. So, I replaced the battery and alternator. Started fine for a few weeks. This is all hit or miss. I replaced the fuel pump in December. It started fine until April. Now it's back to not starting. Sometimes it would and sometimes it wouldn't. It doesn't matter the time of day or how long I've driven it. Now I went to visit my mom the other day and it started fine. I was at her place for a few hours. Again, it wouldn't start. I couldn't hear the pump. About 5 minutes later it started. It idled rough for a few seconds then shut off. Will not start again.
Friday, April 22nd, 2022 AT 4:10 AM

13 Replies

Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
There could be a couple things causing this, but we need to start with finding out what we have for power at the relay when this is happening.

Basically, if it is a new relay and new pump then we can assume for now that they are not the cause.

So that means we need to check for power and ground at the relay when this issue is happening. Clearly if the engine is starting then the issue is most likely not there.

So that means we need to remove the relay and check for ground on the terminal to the PCM. Basically, what is happening is the Fuse 24 from the fuse block on the left side of the dash, is supplying power to the control side of the relay. The PCM grounds the relay on the Brown wire and this causes the contacts in the relay to close sending power from fuse 24 in the engine compartment fuse block to the fuel pump.

https://www.2carpros.com/articles/how-to-check-wiring

The way to check and see if the PCM is grounding the relay is to put your meter on battery positive and then the black lead on this terminal then turns the key on. The meter should read battery voltage if the PCM is grounding the relay.

If not, then the PCM is the issue.

If it is, then we need to check for power from both fuses and then check the wiring to the fuel pump if that all checks out.

Please run through this and let me know what you find with this, and we can go from there.

Thanks
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Friday, April 22nd, 2022 AT 12:38 PM
Tiny
WAYNE69
  • MEMBER
  • 7 POSTS
Hi, here is an update: I contacted a cousin of mine that I see maybe once a year and he works at a place that does tires and mechanic work. He brought with him a scanner, a $1,800.00 scanner. Any ways he didn't find anything. In the meantime, another friend is under the hood and he pulled the fuel pump relay out and pulled the fuse box out of its holder and is moving it around. He put relay back in. My cousin had to check one more thing on the scanner, so he had to turn it over. It started right up. He is just as puzzled as I am. Any thoughts? Thank you for your time.
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Monday, April 25th, 2022 AT 4:02 AM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
One of two things in my mind. If he moved the relay to a different location, then the relay was the issue. If he removed the relay and then reinstalled it and it started right up, then the only thing that makes sense is that it was loose or the contacts in the box were corroded.

Removing it and reinstalling it most likely found a contact point that it didn't have prior.
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Monday, April 25th, 2022 AT 11:35 AM
Tiny
WAYNE69
  • MEMBER
  • 7 POSTS
Thank you for the response. I will investigate it more closely. I will let you know what I find.
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Monday, April 25th, 2022 AT 7:14 PM
Tiny
KASEKENNY
  • MECHANIC
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Sounds great. Let us know what you find with this because it will surely help others that have this issue.
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Monday, April 25th, 2022 AT 7:43 PM
Tiny
WAYNE69
  • MEMBER
  • 7 POSTS
Hi, I took my vehicle to the shop where I get my inspections done. He found the wires at the bottom of the fuse box where the fuel pump fuse and relay are were corroded. He has seen this issue before on some Chrysler products. He also said that he has seen the wires break off due to corrosion. It's running good so far. Thanks for all your help.
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Saturday, April 30th, 2022 AT 4:12 AM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Just to add to this, I have seen that as well. Unfortunately, the water is able to get in and it runs down the harness where it sits in the connector and causes this issue.

I am pretty confident that was your issue. Thanks for the update as that info will definitely help others.

Thanks
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Saturday, April 30th, 2022 AT 5:37 AM
Tiny
WAYNE69
  • MEMBER
  • 7 POSTS
Well, it's back to not starting again. I'm lost. I guess I'm going to have to take it to a dealer and pay big bucks to find out what is going on. The fuel pump isn't getting power. I am not good at wiring tech.
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Sunday, May 8th, 2022 AT 8:11 PM
Tiny
KASEKENNY
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When he found the corrosion, how did he repair it? Can you access that connector and get a picture of inside the connector and then on the underside of the PDC?

More than likely if he just tried to clean it out and put dielectric grease in there, then it is not repaired. More than likely he is going to have to replace the connector and even the PDC if that is not able to be completely cleaned.

Replacing connectors is not that complicated if you feel confident in soldering.

Here is a video that will show exactly how to do it:

https://www.youtube.com/watch?v=PxA5wczsCVo

Clearly this is assuming that this is still the same cause which is likely depending on how they repaired this.
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Monday, May 9th, 2022 AT 6:05 AM
Tiny
WAYNE69
  • MEMBER
  • 7 POSTS
He told me there was some but not that bad. He told me that when I put the new pump in I didn't clear the codes. He did that and he said started right up. I am going to try to do some testing myself. I am not good with wiring, lol.
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Tuesday, May 10th, 2022 AT 9:02 AM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Haha. I understand. Electrical is the hardest thing on vehicles so you are not alone.

Let me know if you have questions as you work through it and let me know what you find.

Thanks
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Tuesday, May 10th, 2022 AT 10:26 AM
Tiny
WAYNE69
  • MEMBER
  • 7 POSTS
Okay, here is what I did so far: I used a test light and the relay and fuse are getting power. I unhooked the wires from the pump and used a battery charger to hook them on to the red and black wires and the pump ran. I also peeled back some of the black wire hooked the wires back on to the pump. I then got gator clips and hooked one end to the black wire from the pump to a good ground. Turned the key and nothing. Pump didn't run. I'm thinking it's the red power wire. Could I have a bad relay or somewhere the red power wire is bad between the fuse box and the pump.
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Tuesday, May 10th, 2022 AT 10:57 AM
Tiny
KASEKENNY
  • MECHANIC
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Just want to make sure I understand because I think you are on the issue.

You checked pin 30 of the fuel pump relay and have 12 volts? If so, jump 30 to 87 and the pump should come on.

If this comes on, then your wiring and pump are fine. This means we will have a relay issue or a control side issue.

The next thing to check is for 12 volts with the key in the on position at pin 86 of the relay. If you have 12 volts here, then we need to check for a good ground on pin 85.

You check for a ground by moving your lead to a 12-volt source and then use this terminal as your ground and turn the key on. Your meter should read 12-volts, or the test light should come on.

See the wiring diagram below for the details on this.
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Tuesday, May 10th, 2022 AT 1:03 PM

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