Jeep No Start – Is it Fuel Pump Relay or Vacuum?

[Mike]

Hey all,

I replaced the PCM in my 1997 Jeep Grand Cherokee (v6) a month ago to fix intermittent stalling/bucking problems while on the highway. Luckily, that problem is now fixed (woo!).

However, I now have a no/slow start condition. Basically when I go to turn the key, the engine “ticks” for about 5-10 seconds before actually turning over and starting. As a quick test for fuel pressure, I decided to turn the key to On and let it sit for a few seconds so the fuel pump can pressurize the system. When I do this, the car starts in about 2-3 seconds so it definitely makes me think it’s fuel pressure related. Once the car is started, she runs fine.

I know the most likely culprit is the fuel pump relay is not keeping pressure on the fuel line after the car is off. I replaced the fuel pump ~9 months ago with an OEM Bosch as part of my troubleshooting of the stalling/bucking problem. As such, I’m doubting this is the cause since it’s a new part and all (the replacement was for the whole assembly – pump, filter, relay, etc.).

Coincidentally, I’m getting a CEL with a P1494 (Leak Detect Pump Pressure Switch). I’ve tried looking into this code and it seems like there is a little EVAP monitoring system that uses vacuum to check for leaks. I’m really unclear how the whole vacuum system in a car works :blush: so I’m not sure if they’re related or not – although they did show up at the same time. I tried looking at all the hoses to see if something got disconnected / is causing a vacuum leak but everything looks fine to me.

Can a vacuum leak cause pressure in the fuel line to decrease while it’s been sitting or are these two independent systems?

I’d like to reiterate that the Jeep drives fine once she’s started and as long as I turn on the key and let the fuel pump run for the 3-5 seconds (I can hear it), she starts up much faster but I still know it’s not ‘right’. Any comments are much appreciated!

Topic

[college man]

actually by your description of slow or ticking.It sounds like
your starter is not engaging or the battery is weak. check your
cables and battery.

http://www.ericthecarguy.com/faq/solving-automotive-electrical-problems

http://www.ericthecarguy.com/faq/solving-automotive-no-start-problems

[Josh]

+1 on above post by CollegeMan. According to my knowledge your fuel pump relay has nothing to do with your fuel pressure, that’s a check valve with in the pump it’s self. But I would check your electrical connections from battery to starter.

[Mike]

I just realized I left out some important information. If the Jeep is off for short durations, she starts right up (go into grocery store, come out and she cranks no problem). It’s only when she’s been sitting for hours (end of day at work, morning before work) that it has this issue.

If it was electrical, I would think I’d have problems all the time? I don’t understand why turning the key to ‘on’ for ~10 seconds would help an electrical problem…can someone exlpain?

BTW, the battery is about a year old and the starter is only 1-2 months old.

[college man]

when you run the vehicle.The battery charge is fresh.
when you leave it the battery shows the problem. Try
this test.check the battery voltage when the starting
symptom happens or jump start the vehicle to see if it
cranks right away.

[Bill]

Repair the Slow/no crank problem and I bet money your other problems will go away.

Have the battery load tested as well as the charging system tested. Check for loose or dirty connections.

[EricTheCarGuy]

+1 Check the battery, cables, starter and charging system before you get into anything else. It sounds like a batter, starter, or connection issue to me.

http://www.ericthecarguy.com/faq/solving-automotive-no-start-problems

[Author]

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