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    Thread: 1991 Mk2 GTI 8v Engine stalls when fuel is below 1/4 after riding for a while

    1. Semi-n00b
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      09-22-2012 04:09 AM #1
      Hello.

      I have a problem with my 1991 Mk2 GTI 8v. After riding for a while with my GTI when I'm low of fuel (less than 1/4, but without getting to the reserve) there's a point when the engine stalls and I can't turn it on until 10-15 minutes. Usually before the engine starts to show symptoms of stalling I can hear a very noisy sound that looks to come from one of the fuel pumps.

      Also when the engine gets hot at normal temperature and I want to accelerate fast the throttle does not response, it does nothing for some seconds (but 10 or more seconds, sometimes it works one second yes, one not, one yes... for a time) until it "works" again.

      I cleaned the ISV, replaced spark plugs, distributor cap and distributor rotor which where in bad condition, but it didn't fix the problem.

      What it can be?

      Thanks for your help.

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      09-22-2012 12:40 PM #2
      Think you need to take a look at the fuel pumps. Could be just one or maybe both are bad/going bad. Most of what you say points to something wrong with the fuel pumps, doubt just the relay.

    3. Semi-n00b
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      09-22-2012 03:04 PM #3
      Quote Originally Posted by WaterWheels View Post
      Think you need to take a look at the fuel pumps. Could be just one or maybe both are bad/going bad. Most of what you say points to something wrong with the fuel pumps, doubt just the relay.
      How I can check them? It's easy? What tools do I need?

      Thank you!

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      09-22-2012 08:29 PM #4
      I don't know how cars were equipped in Spain but in the US they came with a fuel pump in the fuel tank and one in a black box just in front of the rear axle on the passenger side. The in-tank pump runs around $50 US new. It is attached to the fuel sending unit in the gas tank. It is a simple job to replace it using common tools but you do have to work in gasoline. The other fuel pump, located in the black fuel reservoir under the car, goes bad less frequently and is much more expensive (Around $200 US). That pump is also not bad to replace but once again involves working with gasoline.

      Your symptom of working OK until approx 1/4 tank is indicative of a bad in-tank pump. The in-tank pumps go bad often. That is where I would start. One of the in-tank pump failure modes is also intermittant running -- running until getting hot and then shutting down. A failed in-tank pump can also damage the main pump since the main pump operates in a reservoir of gasoline which keeps it cool. If your in-tank pump has failed you may be stressing the main pump and it will soon also fail. I have seen cars with bad in-tank pumps run for a long time as long as the gas tank is kept opver 1/4 tank. Apparently the main pumps can get sufficient fuel for the engine and cooling in that situation.

      You could check the fuel pressure -- there is a test barb at the end of the fuel rail. But if the in-tank pump is working on and off or not at all the main pump might not have enough fuel supply to produce full pressure. There is also a flow test that can be done with the in-tank pump to see if it is pumping enough gas. I usually just flow the pump output into a spare gas can instead of trying to measure quantity.

      The fuel system has a timed shut off after a few seconds if the engine is not running so the fuel pump relay is pulled and the two large perpindicular slots under it jumpered for test purposes. FR

    5. Semi-n00b
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      09-23-2012 05:30 AM #5
      Quote Originally Posted by Fat Rabbit View Post
      I don't know how cars were equipped in Spain but in the US they came with a fuel pump in the fuel tank and one in a black box just in front of the rear axle on the passenger side. The in-tank pump runs around $50 US new. It is attached to the fuel sending unit in the gas tank. It is a simple job to replace it using common tools but you do have to work in gasoline. The other fuel pump, located in the black fuel reservoir under the car, goes bad less frequently and is much more expensive (Around $200 US). That pump is also not bad to replace but once again involves working with gasoline.

      Your symptom of working OK until approx 1/4 tank is indicative of a bad in-tank pump. The in-tank pumps go bad often. That is where I would start. One of the in-tank pump failure modes is also intermittant running -- running until getting hot and then shutting down. A failed in-tank pump can also damage the main pump since the main pump operates in a reservoir of gasoline which keeps it cool. If your in-tank pump has failed you may be stressing the main pump and it will soon also fail. I have seen cars with bad in-tank pumps run for a long time as long as the gas tank is kept opver 1/4 tank. Apparently the main pumps can get sufficient fuel for the engine and cooling in that situation.

      You could check the fuel pressure -- there is a test barb at the end of the fuel rail. But if the in-tank pump is working on and off or not at all the main pump might not have enough fuel supply to produce full pressure. There is also a flow test that can be done with the in-tank pump to see if it is pumping enough gas. I usually just flow the pump output into a spare gas can instead of trying to measure quantity.

      The fuel system has a timed shut off after a few seconds if the engine is not running so the fuel pump relay is pulled and the two large perpindicular slots under it jumpered for test purposes. FR
      First thank you for your answer.

      Actually I don't know if my golf has 1 or 2 fuel pumps. I'll confirm the number of pumps later to be sure.

      Looking in a car parts webpage I can see some pumps with a great difference of price, some cost around 70-90€ an others arround 250€ so I can suposse Spanish Golfs have 2 pumps...

      For now I'll try with the fuel filter replacement with the hope that it will fix the problem .

      Best regards!

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      09-23-2012 12:45 PM #6
      Quote Originally Posted by dani91gti View Post
      Actually I don't know if my golf has 1 or 2 fuel pumps. I'll confirm the number of pumps later to be sure.
      Except for unimportant things, like trim items, your car is the same as the North American version. So yes, it has two pumps and uses the same pumps (part number).

    7. Semi-n00b
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      09-23-2012 02:45 PM #7
      Quote Originally Posted by WaterWheels View Post
      Except for unimportant things, like trim items, your car is the same as the North American version. So yes, it has two pumps and uses the same pumps (part number).
      That's correct. I've crouched under the car to look if there was a fuel pump and it was there under the car.

      The pump inside the fuel tank is low pressure and the other is the high pressure, right?

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      09-23-2012 05:34 PM #8
      Right. But Digifant cars didn't have the high pressure pumps required of CIS cars. The in-tank pump is simply a transfer pump from the gas tank to the main pump fuel reservoir.

      Test flow the in-tank pump and see what you get. The pump is accessed through a round access panel in the rear hatch floor. I usually simply disconnect the fuel line, connect a fuel line of an appropriate size and then aim the line into a gas can or other container. Connect the pump to a 12V DC power supply and watch it flow. In 10 seconds the pump should deliver 300 cc of fuel (10 oz). I rarely measure the flow. If the flow is strong the pump is ok -- if it dribbles or has a weak flow replace it. One other test I usually perform is to jumper the fuel pump relay and test for 12V DC at the fuel pump. FR

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      09-23-2012 06:13 PM #9
      Quick and dirty would be to see if you can hear the in-tank pump. If not, you've found the problem. If you can hear it, it'd require further investigation.

      Sometimes the pickup tubes for the in-tank pump rot away as well. When you pull the pump out, you'll be able to gauge if they need attention.

      At least the in-tank pump is the cheaper one, and you have a door to access it.

      Generally, using two flathead screwdrivers crossed together can get it open.
      I really suck at smog.

    10. Semi-n00b
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      09-24-2012 05:07 AM #10
      Actually I hear the fuel pump. When it's working ok the sound is not noisy but can be heard easy. When the car is about to stall the pump is really noisy.

      This morning I filled the fuel tank a bit more of half and I gone to twisty roads in the nearby mountains to test the car (I went quite fast and strong) and then some freeway and the car worked fine.

      I don't have changed the fuel filter yet.

      Looks like the cause of car failure is located, everything aims to the fuel pump.

      For now, as I said, I'll change the fuel filter and keep testing with the fuel tank at more than half and if that doesn't fix the problem I'll replace the fuel tank pump.

      Thanks everyone for your help and my apologies if my English is poor.

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      09-27-2012 07:31 PM #11
      Having more gas in the tank makes the life of the in-tank pump easier for sure and may provide enough of a hydraulic head to supply the main pump without the in-tank pump even operating.

      Since both pumps depend on being immersed in gasoline for cooling -- your in-tank pump may well be complaining full time and overheating when the gas level is below 1/4 tank. Lack of sufficient fuel over time will also harm the main pump and that pump will have to be replaced.

      As a general "rule" I never let my gas tank get too far below 1/4 tank to protect the fuel pump(s).
      After the initial investment, it costs no more to maintain a gas tank at half full than to keep it closer to empty. FR

    12. Semi-n00b
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      10-02-2012 03:51 PM #12
      Hello again! I have new news and more questions.

      I replaced the fuel filter and I have done some test on the car. Looks like it functions better, but it still stalls when it wants and it's still being a but "unstable". This time I've gone around the city with heavy traffic (the worst) and worked for one hour with heavy traffic, then it stalls for 5 minutes and then it engaged (15 seconds of start engine :/ ) and worked for 20 more minutes until I get home.

      Another thing I discovered, but I'm not sure, is that the blue coolant sensor (ECS) is faulty or something because when I unplug it nothing happens and as I know when you disconnect it the RPM increase. This has been done with the engine in cold temperature, and the engine idle was at 950 rpm (a bit unstable with bad sound).

      Can be possible that blue sensor is the source of some problems? I checked the resistance of the sensor in cold (25ºC) and it was 2010 Ohms.

      Thank you!
      Last edited by dani91gti; 10-02-2012 at 03:54 PM.

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      10-02-2012 09:47 PM #13
      The 2100 Ohms sounds about right for the 25C temp. More important is that the temp sensor resistance varies with the temperature of the engine. With the engine hot the resistance should be 200-300 Ohms. Those blue sensors cost less than $20 US. They are very easy to replace -- make sure you use a new "O" ring gasket and be sure to remove the old gasket from the hole. Leave the cooling system sealed and remove the old one and replace it with the new one quickly. Do it with the engine overnight cold. A small amount of coolant will spill so be sure to have a catch pan for it.
      Top up the coolant if need be.

      I continue to think you have fuel pump issues especially based on the FP noises you reported. Running on and off is a fuel pump failure mode. They run for a while and then shut down when they get hot then will work again after they cool off. However, that symptom could also be indicative of a bad fuel pump relay or even a Digifant Relay. The relays have a similar failure mode. (Run for awhile -- get hot -- shut down -- cool off -- run for a while.) FR

    14. Semi-n00b
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      10-03-2012 07:39 AM #14
      Quote Originally Posted by Fat Rabbit View Post
      The 2100 Ohms sounds about right for the 25C temp. More important is that the temp sensor resistance varies with the temperature of the engine. With the engine hot the resistance should be 200-300 Ohms. Those blue sensors cost less than $20 US. They are very easy to replace -- make sure you use a new "O" ring gasket and be sure to remove the old gasket from the hole. Leave the cooling system sealed and remove the old one and replace it with the new one quickly. Do it with the engine overnight cold. A small amount of coolant will spill so be sure to have a catch pan for it.
      Top up the coolant if need be.

      I continue to think you have fuel pump issues especially based on the FP noises you reported. Running on and off is a fuel pump failure mode. They run for a while and then shut down when they get hot then will work again after they cool off. However, that symptom could also be indicative of a bad fuel pump relay or even a Digifant Relay. The relays have a similar failure mode. (Run for awhile -- get hot -- shut down -- cool off -- run for a while.) FR
      Ok! I take note.

      I'll replace the Fuel pump, the relay and the blue sensor + o-ring gasket.

      Thanks!

    15. Semi-n00b
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      10-03-2012 08:14 AM #15
      Quote Originally Posted by dani91gti View Post
      Ok! I take note.

      I'll replace the Fuel pump, the relay and the blue sensor + o-ring gasket.

      Thanks!
      Sorry, I forgot to ask before.

      ¿Where is that relay located?

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      10-03-2012 06:40 PM #16
      Check / replace the in-tank transfer pump and associated hoses before anything else.

      If the main pump is going noisy before stalling, the fuel pump relay should be fine.

      CTS is of no concern at the moment. If of interest, check to see that you are in closed loop when warm (voltmeter to o2 sensor to check for oscillation). If it drives sluggishly until it's warmed up, CTS may be of interest.
      I really suck at smog.

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      10-04-2012 10:06 AM #17
      Just do the in-tank fuel pump. As Ziddey states (and as I have stated several times) the fuel pump noise you report is a good indicator that is where your issues are.

      To answer your question: The fuel pump relay is on the fuse and relay panel -- lower right corner -- first relay row above the fuses. Look for a PN like 191 906 383. Here in the US they can be purchased on line for well under $10. I always used to carry a spare. FR

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      10-04-2012 02:10 PM #18
      Hello again!

      Just now I come from try to remove the fuel tank pump. I say "try" because I can't do it.

      I can't turn the black plastic ring.

      ¿Do I need a special tool or something?

      Anothing thing I found, but I'm not sure if it's normal or not, it's a transparent yellowish tube along side the 2 pump tubes. What is supposed that tube to do?

      Here is a pic. Sorry for bad quality.

      http://i50.tinypic.com/111ujhs.jpg

      PS: When I removed the fuel hoses only 2 petrol drops fell from them. I expected more petrol to drop, Is it normal?
      Last edited by dani91gti; 10-04-2012 at 02:25 PM.

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      10-04-2012 03:29 PM #19
      You should see two notches on the ring. Take two flathead screwdrivers and form an X to open it.

      Can't see the other hose too well in the picture, but I'm imagining it's for the evap system?
      I really suck at smog.

    20. Semi-n00b
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      10-04-2012 04:19 PM #20
      Quote Originally Posted by ziddey View Post
      You should see two notches on the ring. Take two flathead screwdrivers and form an X to open it.

      Can't see the other hose too well in the picture, but I'm imagining it's for the evap system?
      I'll take a look at those notches tomorrow with better lightning (daylight).

      Thanks.

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      10-05-2012 02:23 AM #21
      Pump dismounted. I just had to use my abilities with the screwdriver and the jack on those notches.

      I found an strange residue on the pump intake aside from various granular particles.

      Here are the pictures:





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      10-05-2012 10:09 PM #22
      The fuel pick-up strainer looks pretty good. You might want to use a flashlight and take a look inside the gas tank to see how much crud is in there. If there is a lot of stuff floating around in the tank you might want to remove the tank from the car and clean it out.

      Mount the new pump in place of the old and reassemble. Use new hose clamps in place of any you have had to remove. Make sure that the pump fits well on the assembly so it doesn't leak. FR

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      10-07-2012 02:22 PM #23


      Today I tested the fuel pump and simply doesn't work, no sound or movement when I put +12v to it (red wire = + and brown = - and test vice versa too). I checked continuity of everything and all plugs or internal wires are OK. When you put +12v to the pump it should have started to work, even on a dry environment, right?

      Can the 3.5 Bar fuel pump deliver fuel when the in-tank pump is completly broken?

      Tomorrow I'll get a pressure meter so I can check the fuel presure. I'll mount everything and check the presure of the fuel ramp.

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      10-07-2012 03:55 PM #24
      yep, change that pump and you'll be good to go
      I really suck at smog.

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      10-07-2012 04:13 PM #25
      Quote Originally Posted by ziddey View Post
      yep, change that pump and you'll be good to go
      Ok! I'll change the tank pump. Just wanted to be sure.

      Thanks!

      Hey but if the tank fuel pump was dead how was able the other pump to get fuel? The plastic box near the fuel filter is an small reservoir from where the 3.5Bar pump gets the fuel, and that small reservoir is filled thanks to the in-tank pump, right?
      Last edited by dani91gti; 10-07-2012 at 05:27 PM.

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      10-07-2012 07:33 PM #26
      I answered your question in a pervious post -- The symptom you reported "engine stalls when fuel is below 1/4" indicates a bad in-tank fuel pump.

      Quite commonly the car will run with over 1/4 tank because of gravity flow (syphon) from the tank to the reservoir and perhaps some suction from the reservoir as the fuel pump empties it. With around 1/4 tank of fuel the reservoir can't keep itself full from gravity and/or suction as there is not enough "potential" between the fuel in the tank and the fuel reservoir.

      With a bad in-tank pump the main pump will struggle to supply fuel and will eventually burn out. In fact, you may have damaged your main pump by not replacing your in-tank pump sooner. The louder fuel pump sound you were hearing was likely the main pump struggling to deliver fuel. Time will tell. FR

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      10-09-2012 08:52 AM #27
      Pump replaced, no leaks, I can hear the pump and it sounds OK. When the car is idle sometimes I can smell gasoline, like a too rich mixture or something, but that's in cold and I don't know if it happens at work temperature or if it's normal.

      By the way, the engine sound, in my opinion, it's not good enough... I have to hear it when the car is hot and use the car for a time because I just turn on the engine for 5 minutes and see that works.

      Maybe the "broken" knock sensor has something to do?

      The fuel pump brand is "Meat & Doria Special parts" and it's fabricated in the P.R.C. so probably is bad quality but if it works...

      Later I'll do a pressure check.

      I fell I've done nothing

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