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Old 06-07-2011, 02:59 AM
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WJ Gremlin(s) - Starting and Fuel Pressure

I have a 2003 Grand Cherokee 4.7 with some starting problems. I'm not sure if the problems are related or possibly symptoms of something else, but I would dearly appreciate your comments/advice as I have thrown quite a bit of money at the problem so far and it has not been resolved yet.

My problems:

1. It almost never starts first time
When the Jeep cranks in the mornings in almost never starts when cranking it the first time. If I keep cranking it for like 15-20 seconds then eventually it will start.
If however I only crank it for like 1-2 seconds the first time, it will almost immediately start when cranking it thereafter.

2. It is dead after a cold night
Every morning after a cold night the Jeep will be completely dead the following morning. If I turn the key absolutely nothing happens. I can't hear a click/buzz/sound nothing. I found out if I then disconnect the battery negative terminal for a few seconds and then reconnect it, it will start almost immediately.

Work done so far:
- Replaced battery
- Replaced starter
- Replaced spark plugs

Problem 1 sounds like a fuel pressure related problem (possibly fuel filter/regulator, o-rings, fuel pump ?). It is slightly irritating, but I can live with this one until the next service.

Problem 2 is however a major irritation that I would like to resolve, but I have not read anything quite definitive about possible solutions. My mechanic now want to possibly replace :
- Crank position sensor
- Transmission position sensor
- Throttle position sensor
- And some other sensors also ...

But from what I read it can be related to other electrical issues also, especially grounding. I have measure the voltages in my engine bay as follows:
- Battery negative to engine block - 0.035 V
- Battery negative to body work - 0.016 V
- Engine block to body work - 0.048 V
Apparently the last measurement should be less than 0.02 and possibly indicates a grounding/contact problem on some cables.

Any ideas guys ?!
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Old 06-07-2011, 09:19 AM
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Re: WJ Gremlin(s) - Starting and Fuel Pressure

Regarding item 1, will it start quickly when you just put the ignition switch in on for 3 sec, switch it in off again and then try to start? A new filter/regulator would also be my first step on this one.
Regarding item 2, when you say its completely dead, you mean that also no indication lights will light up when you put the ignition switch in run? I would suspect more the ignition switch to be fault then any sensor. With sensor faults at least the fuel pump should run and normally the engine would crank as well.
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Old 06-07-2011, 10:37 AM
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Re: WJ Gremlin(s) - Starting and Fuel Pressure

1. Yip, when I "prime" the car it start a lot easier, but I have replaced the filter/regulator. Would the next step be fuel pump or perhaps the o-ring ?

2. Dead as in when I turn the key absolutely nothing happens. Nothing turns, clicks whatsoever. However, the dash indication lights still work as normal, also the lights, fan etc. So power to the electronics does not seem to be the problem.
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Old 06-07-2011, 12:02 PM
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Re: WJ Gremlin(s) - Starting and Fuel Pressure

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Originally Posted by 0l1v3r View Post
1. Yip, when I "prime" the car it start a lot easier, but I have replaced the filter/regulator. Would the next step be fuel pump or perhaps the o-ring ?
My next step would be fuel pump and injectors. Have you checked your fuel pressure?
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Old 06-07-2011, 01:13 PM
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Re: WJ Gremlin(s) - Starting and Fuel Pressure

Not yet, will have it done when I have problem 2 attended to : Any chance that it might just be the starter relay ? Does a WJ have such a thing ?
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Old 06-07-2011, 01:35 PM
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Re: WJ Gremlin(s) - Starting and Fuel Pressure

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Originally Posted by 0l1v3r View Post
Not yet, will have it done when I have problem 2 attended to : Any chance that it might just be the starter relay ? Does a WJ have such a thing ?
The WJ does have a starter solenoid. It should be on the starter motor.
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Old 06-07-2011, 02:15 PM
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Re: WJ Gremlin(s) - Starting and Fuel Pressure

Before changing any component you can better troubleshoot a bit more. You say that you donīt hear anything when you turn the ignition switch. The first thing that should happen when you put the ignition switch in run, is that the fuel pump should run for 3 sec. (so with engine off). Let someone help you and let him (or her) listen close to the fuel tank at the lower side. You could also remove the fuel cap, but you should hear a low volume buzzing sound from the pump for the first 3 sec. If this is ok, then probably your ignition switch is ok.
There is a starter relay and a starter solenoid. The solenoid is on the starter itself and it switches the high starter current and connects the starter motor to the engine. The starter relay is a small one in the power distribution center under the hood, next to the battery. This small relay switches the starter solenoid. When you open the PDC, you can see on the inner side of the cap on which position is the starter relay. Its the same as the wiper relay, fuel pump relay, airco relay and horn relay. Just swap it, test it and let us know.
Regarding the fuel pump, first check the fuel pressure at the rail. If thats out of specifications, the next step would be to lower the tank and check the fuel pump/seal/internal filter. Depending on how many miles you have on it, it could be wise to just change the pump.
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Old 06-07-2011, 03:27 PM
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Re: WJ Gremlin(s) - Starting and Fuel Pressure

Thanks for the advice guys ! Here's hoping to a cold night so that I can try to swap out the relays and test it ....
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Old 06-12-2011, 04:03 PM
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Re: WJ Gremlin(s) - Starting and Fuel Pressure

your fuel pressure issue will be a check valve in your pump, when you shut it off it dumps all the pressure back into the tank causing a lack of prime on the first start. Of course it would be easier to know throwing a fuel pressure gauge on it. Also not that it doesnt happen, but I see fuel pumps dump pressure about 100 of 100 times that you have a pressure relief problem in your fuel system, theoretically an injector could stick open but even then it would be a mist not a DUMP. Still a possibility none the less.

on your no starting issue... next time it does it, apply the brake and cycle the PRNDL from park to low and back to park and make sure its firmly seated in park, try to start it, if it doesnt start still, move the shifter to N and try again... that will aid in ruling out a park/neutral safety switch.

right now on problem 2 I would lean away from all other repair suggestions from your mechanic... none of those inhibit starting functions.... running functions yes, but not starting.
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Old 06-14-2011, 02:22 PM
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Re: WJ Gremlin(s) - Starting and Fuel Pressure

Last time it did the non-starting issue with me I tried the brake/cycle through PRNDL and none of it worked. Neither did it start in N with my foot on the brake. So I guess it at least rules out that switch.

We have not had a cold night yet since my post, so I do not really know if the problem still persists. On this thread though (http://forums.automotive.com/70/6208...lem/index.html) someone mentioned that your voltages in your engine bay should measure no more than :
0.04V (Battery negative to Engine Block)
0.02V (Battery negative to Body)
0.02V (Engine block to Body)

Mine measured as 0.032, 0.016 and 0.048 V respectively.

The 0.048 was looking a bit dodgy, so I had an auto electrician work on it. They replaced my battery terminals, replaced the battery to engine block earth cable and "renewed" the block to body cable. They also replaced the starter relay.

My new measurements are 0.018, 0.01 and 0.031 V respectively.

I'm still holding thumbs for a really cold night soon ....
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Old 07-06-2011, 01:19 PM
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Re: WJ Gremlin(s) - Starting and Fuel Pressure

Quick update. We had some really cold nights here this last week and my WJ still started every morning. So hopefully that problem is now history ...
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