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-   -   2001 Grand Cherokee 4.7L Hard Start (http://www.jeepgarage.org/f203/2001-grand-cherokee-4-7l-hard-start-62674.html)

JEEPSTER49 07-11-2013 07:08 AM

2001 Grand Cherokee 4.7L Hard Start
 
i have a 2001 Grand Cherokee 4.7L. it has developed difficulty in starting. always starts by 3rd turn of the key, hot or cold. i have gotten several opinions, including crank position sensor, temperature sensor, fuel pressure something or other. i don't want to just throw money at this problem. somebody out there must have experienced this problem, so am looking to forum to get the CORRECT answer before i start doing process of elimination. Thanks.

Frango100 07-11-2013 07:51 AM

Re: 2001 Grand Cherokee 4.7L Hard Start
 
Welcome to the garage.
Hard starting can have several reasons and can be difficult to pinpoint.
Fuel pressure would be my first item to check. No need to put a fuel pressure indicator on it yet. There is a schräder valve on the fuel rail (on mine it has a green cap), which you can open by pressing the valve core. Do this on a cold engine before switching the ignition on. Use a rag and check if fuel under pressure comes out. No fuel or almost no pressure could mean a problem with the fuel filter/pressure regulator or a seal in the fuel pump assy. Before next engine start, just try to prime the fuel system first; ignition switch from off to run, wait 3 seconds, back to off and run again and wait 3 seconds, back to off and run again and then start. If it then starts normally, you have a problem with the fuel pressure and i would start changing the fuel filter/pressure regulator.
Also check if there is any fault set in the PCM doing the key dance: ignition switch off/on three times and leave in on at the third time. the odometer will show DONE or any fault code. Let us know what you find.

CheapJeep82 07-14-2013 11:24 PM

Hi jeepster and the garage

I have the same problem. 7-10 sec crank then it stutters to life. Have replaced the crank pos sensor as a mil code came up on the dash. Didn't fix the problem also replaced the cam angle and fuel filter/regulator still no go. I find the 3 prime method sometimes works.
To me it seems as it over fuelling as there is an extremely strong fuel smell from the exhaust.
I've checked the IAC and cleaned, tps is also within manufacturers specs. Any new ideas would be greatly appreciated

Cheers

Frango100 07-15-2013 11:07 AM

Re: 2001 Grand Cherokee 4.7L Hard Start
 
Hi Kent. When i´m not wrong an other member had a problem like this and after he changed the coolant temperature sensor the problem was solved. I will see if i can find that thread.

Dirish1 07-15-2013 04:33 PM

Re: 2001 Grand Cherokee 4.7L Hard Start
 
MY 02 limited did this to me also. I could trun the key to RUN then Off Then Run about 6 times. and it started up just fine.

Change Fuel filter NOTHING
Cleaned Idle Air Valve NOTHING
Change TPS sensor NOTHING
Changed Coolant sensor NOTHING

Changed Fuel pump Assembly (It was like the entire thing not just a pump)
FIXED IT FOR ME.

I changed all the other stuff because people suggested it and I was dreading changing my fuel pump. At least I have new parts.

CheapJeep82 07-15-2013 04:52 PM

Quote:

Originally Posted by Dirish1 (Post 858723)
MY 02 limited did this to me also. I could trun the key to RUN then Off Then Run about 6 times. and it started up just fine.

Change Fuel filter NOTHING
Cleaned Idle Air Valve NOTHING
Change TPS sensor NOTHING
Changed Coolant sensor NOTHING

Changed Fuel pump Assembly (It was like the entire thing not just a pump)
FIXED IT FOR ME.

I changed all the other stuff because people suggested it and I was dreading changing my fuel pump. At least I have new parts.

That's what I'm dreading a new fuel pump assembly.

CheapJeep82 07-15-2013 04:55 PM

Quote:

Originally Posted by Frango100 (Post 858531)
Hi Kent. When i´m not wrong an other member had a problem like this and after he changed the coolant temperature sensor the problem was solved. I will see if i can find that thread.

Hey Frango

How is the coolant sensor tied into the start system.

Frango100 07-15-2013 04:59 PM

Re: 2001 Grand Cherokee 4.7L Hard Start
 
Probably best would be to check the fuel pressure at the rail, should be around 49 psi. Then check the pressure drop (ignition switch in off) over 5 minutes time. If the pressure went down to less then 30 psi after 5 minutes, then you could have a leaking o´ring in the fuel pump assy. This o´ring could let the fuel drain back into the tank and at next startup there will be a column of air in the line.
There is s TSB about this and they have (or at least had) a repair kit with this o´ring, so that not the whole fuel pump module needs to be replaced. See here: http://www.wjjeeps.com/tsb/tsb_wj_1400201.pdf
Normally a bad fuel pump or doesn´t work at all, or starts delivering less pressure or the pressure drops when the flow increases. This will be felt more during acceleration or high speeds, when more fuel is needed.

Dirish1 07-15-2013 05:02 PM

Re: 2001 Grand Cherokee 4.7L Hard Start
 
Quote:

Originally Posted by CheapJeep82 (Post 858740)
Hey Frango

How is the coolant sensor tied into the start system.

The WJ computer changes the idle air and throttle position and some other crap like that if the engine is already warm Vs cold. If the sensor is bad and reading a warm engine when it is not it will make the changes as if it was warmed up but its actually a cold start making it hard to start.

Dirish1 07-15-2013 05:10 PM

Re: 2001 Grand Cherokee 4.7L Hard Start
 
Quote:

Originally Posted by Frango100 (Post 858743)
There is s TSB about this and they have (or at least had) a repair kit with this o´ring, so that not the whole fuel pump module needs to be replaced. See here: http://www.wjjeeps.com/tsb/tsb_wj_1400201.pdf
[/FONT]

Autozone, O-Rielys, and Advanced LOLed @ me when I asked about this. But I figured if I was dropping my tank after 115,000 miles I may as well change the whole thing and not have to worry about other parts going bad latter and having to drop the tank again.

Still waiting on my post to get approved to fix my problem. I have to wait because I am new?

Frango100 07-15-2013 05:17 PM

Re: 2001 Grand Cherokee 4.7L Hard Start
 
Quote:

Originally Posted by Dirish1 (Post 858745)
The WJ computer changes the idle air and throttle position and some other crap like that if the engine is already warm Vs cold. If the sensor is bad and reading a warm engine when it is not it will make the changes as if it was warmed up but its actually a cold start making it hard to start.

This is partly true. The engine coolant temperature signal is used by the PCM to calculate the fuel injector pulse width, spark advance, the idle air motor position and fuel prime shot pulse width. Throttle position will not be changed though.
You mentioned the strong fuel smell at startup, so there is fuel, but maybe not under the right pressure. I would start doing the fuel pressure check first.
Also when a new fuel pump is needed, you could just change the fuel pump cartidge and not the whole module. Will be significantly less expensive.

CheapJeep82 07-15-2013 05:25 PM

Quote:

Originally Posted by Frango100 (Post 858743)
Probably best would be to check the fuel pressure at the rail, should be around 49 psi. Then check the pressure drop (ignition switch in off) over 5 minutes time. If the pressure went down to less then 30 psi after 5 minutes, then you could have a leaking o´ring in the fuel pump assy. This o´ring could let the fuel drain back into the tank and at next startup there will be a column of air in the line.
There is s TSB about this and they have (or at least had) a repair kit with this o´ring, so that not the whole fuel pump module needs to be replaced. See here: http://www.wjjeeps.com/tsb/tsb_wj_1400201.pdf
Normally a bad fuel pump or doesn´t work at all, or starts delivering less pressure or the pressure drops when the flow increases. This will be felt more during acceleration or high speeds, when more fuel is needed.

Had the o'ring changed a few months back as it was stalling in park or neutral every now and then. Sorry should have mentioned that earlier. Car runs fine once started.


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