Loss of power when towing WJ





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  1. #1
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    Default Loss of power when towing WJ

    We are trying to find a reason for power when towing. The first time was about 6 months ago. When driving without a van there is never an issue. Locking the over drive gears out has helped a lot excluding today. Engine will not rev more than about 1500 RPM. Can drop down to 1000 and go up to 2000. I doubt that it is transmission limp mode as that should be on 2nd gear. I can go to first and seems to work also 3rd. Normally trouble starts after longish drive and when the tank is under half full. We learned not to use overdrive and this approach was confirmed yesterday by multitasking workshop manager in Springbok. "Do not tow with overdrive on. Known issue on WJ."

    Today there were mountain passes and problem got worse. Drove the last 30 km to Velddrif at about 40 km/h. Most of the time short stopping has helped. When stopped engine revs easily to max revs. This revving actually has cleared the problem several times. Today I did get error codes 171/174 (Fuel lean). I have had 161 and 158 for years. Those are for oxygen sensor related. Quite a lot of work was done on those two but they are there.

    Current main suspect is fuel starvation = fuel pump. SWAMBO has had similar problem many years back on their vehicle. That was fuel filter blocking. According to the workshop manual in WJ it is not a service part. When towing the fuel consumption is higher, on long drive the fuel pump may heat up and bypass more. Filter pressure regulator failure/block could also be an issue. Fuel pressure was measured. It was OK but it was tested when car was not towing. I cannot test on the road

    Has anybody had something similar? Any comments?
    Jouko
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    2003 Grand Cherokee 4.7l
    2012 Smart
    Never drive a normal car 8)

  2. #2
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    Default Re: Loss of power when towing WJ

    Maybe call Bulli?
    ASPW on the Jeep Grand Cherokee: "This vehicle is phenomenal... I have never seen a traction control system working quite like this..."


  3. #3
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    Default Re: Loss of power when towing WJ

    My experience is on the very old Isuzu, so take that into account.

    It does sound like a fuel related issue:
    In the Suuz it would usually be air in the diesel piping between tank and fuel pump or (and don't laugh) a vacuum being caused in the fuel tank(s) due to the breather pipe from the tank getting blocked by dust or whatever causing a vacuum build up inhibiting the fuel flow.

    Alt. Bleed the injectors - maybe air in the injectors ?

    It is running but not revving when under load seems like a fuel supply problem.

    But your engine is aeons ahead of my old 280 Diesel so may be other factors there.
    Peter Hutchison
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  4. #4
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    Default Re: Loss of power when towing WJ

    I am talking to Bulli. He suspects petrol pump. I was just now driving with a mechanic. Jeep went to no power mode today without any van. That was the first time. Luckily also when mechanic was with and computer connected. No error codes. They will build something to be able to measure the fuel pressure while driving. We were testing various things. When in no power and I press throttle engine cuts out. Was running on 1500 rev. Issue will not start on downhill. Going from uphill to downhill on no power allows revs to go up at least to 2000.

    Pump is in the tank. Take bumper, tow bar and armor plate off and after market 3 bar pump is no good so worth to try to confirm real reason.
    Jouko
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    2012 Smart
    Never drive a normal car 8)

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    Default Re: Loss of power when towing WJ

    Good luck, crappy thing to happen while on holiday.
    ASPW on the Jeep Grand Cherokee: "This vehicle is phenomenal... I have never seen a traction control system working quite like this..."


  6. #6
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    Default Re: Loss of power when towing WJ

    Fuel pressure sensor? The ECU will make the pump back off if it thinks the fuel pressure is too high.
    Jakes Louw
    2012 Jeep Sahara Unlimited 3.6 V6
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  8. #7
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    Default Re: Loss of power when towing WJ

    Quote Originally Posted by Rainier Vermaak View Post
    Good luck, crappy thing to happen while on holiday.
    Thanks. Not really that big issue. I always expect something happening. I have my office with me and we are not in a hurry. There is family in this town and caravan park is neat and cheap.

    Quote Originally Posted by jelo View Post
    Fuel pressure sensor? The ECU will make the pump back off if it thinks the fuel pressure is too high.
    Thanks. Good to know. If the filter/fuel pressure regulator is failing it could cause pressure issues. Only issue is that there are no error codes.
    Jouko
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    2012 Smart
    Never drive a normal car 8)

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    Default Re: Loss of power when towing WJ

    I would first look at the fuel filter. You would be surprised how many times these are never replaced.
    Brandt Theunissen
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  11. #9
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    Default Re: Loss of power when towing WJ

    We will look at this. In this car it is not a service part. Filter is combined with pressure regulator. If the fuel pressure is low I would take that out first to check. SWAMBO had filter in Nissan 3l hidden in small compartment in a wheel well. Totally unknown to all but one person who told about it. I had endless problems with my first car in SA. Golf 1. Carburetor blocking.. Dealer did not change the tiny inline filter as VW had no part number for it. Then work mate told go and get one from Midas or similar. Early days with alcohol petrol mixes. That time big problems with filters etc.

    Quote Originally Posted by Koebelwagen View Post
    I would first look at the fuel filter. You would be surprised how many times these are never replaced.
    Jouko
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    2012 Smart
    Never drive a normal car 8)

  12. #10
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    Default Re: Loss of power when towing WJ

    If the jeep is on a weak spot remove the fuel cap and see if their is a difference. Faulty fuek cap can cause the same issues if you get a vacuum in the tank.
    Bernhard Whitehead
    aka Bere

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  14. #11
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    Default Re: Loss of power when towing WJ

    We did this and drilled 2 mm holes to the gap to make sure. Not the issue. We have had this on 2 other cars.

    Quote Originally Posted by Bere View Post
    If the jeep is on a weak spot remove the fuel cap and see if their is a difference. Faulty fuek cap can cause the same issues if you get a vacuum in the tank.
    Jouko
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    Never drive a normal car 8)

  15. #12
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    Default Re: Loss of power when towing WJ

    Talking through my ear here but we had the same issue with my 2.3 Microbus only when towing a few times.
    Turned out to be one cylinder flooding with petrol and a 20 minute rest cured it.
    Always on Van Reeenens.
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  17. #13
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    Default Re: Loss of power when towing WJ

    Mechanic was able to measure the fuel pressure when the fault occurred. Pressure dropped. Pump was replaced but more suspect is O ring in the housing. Pump is only about R700 and easy to get. Total cost R2139.00 including testing and labor for 3 hours. Issue seems to have been solved.

    There are sensor combinations that can give very similar problem as I had. Better to have pump issue than sensor issue.
    Jouko
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    2012 Smart
    Never drive a normal car 8)

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  19. #14
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    Default Re: Loss of power when towing WJ

    Did you not get the memo about how expensive Jeeps are to maintain or repair?
    ASPW on the Jeep Grand Cherokee: "This vehicle is phenomenal... I have never seen a traction control system working quite like this..."


  20. #15
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    Default Re: Loss of power when towing WJ

    Mercedes is sending me day after day "Bring your car using our special hourly rate R550 plus VAT. Repair was done under R400 plus VAT

    Tomorrow I get 4 new tires Good Year Wrangler AT Adv for about R2100 incl/tire. T&M gave extra discount as they are for Jeep

    Old Jeep is cheaper to maintain than new car with maintenance plan. I have no need or reason to take financial deal over 7 years like many do to pay for the first service

    This repair place over charged me. They promised to charge only 2.5 hour labor. They charged 3. Maybe they used that extra half an hour to fit the bumper properly. It was not right when I took the car in.


    Quote Originally Posted by Rainier Vermaak View Post
    Did you not get the memo about how expensive Jeeps are to maintain or repair?
    Jouko
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    2003 Grand Cherokee 4.7l
    2012 Smart
    Never drive a normal car 8)

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