Suddenly lost prime under power??? - page 1 - Troubleshooting - VWDiesel.net The IDI, TDI, and mTDI source.

• Suddenly lost prime under power??? by leprechan on 04 May, 2004 18:30
• I have a 91 na Jetta and it suddenly started sputtering and lost all power while driving.  I was test driving after replacing a main shaft seal on the injection pump.  It ran fine and drove well for a good 40 minutes and then that happened.  The inlet line to the pump had tons of air in it and the fuel left in the line was not moving.  I've checked for clogs and everything seems fine through all the lines.  I've blown air through all the lines with and air compressor and didn't see any chuncks come out.  I've replaced the filter and both lines from the filter to the pump, but it still does the same.  I though the vane pump might be going so I put an electric pump between the filter and the injection pump but it still did the same thing.  I've looked at the water sepparator underneath the rear passenger door and very little water came out before it turned to fuel.  The check valve is still good as well.  I've suspected that it might be sucking air from a leak in the water separator, but I'm not sure.  I haven't had time to go bypass the water separator yet, but I won't be able to work on it until this weekend.  Thanks for any helpful advice.
• #1 by Anonymous on 05 May, 2004 07:14
• it is very odd that you are having this problem on that car, it has plastic fuel lines that are usually very durable.  are you running diesel or bio-diesel?  check the o ring under the fuel return/heater on the filter ( the line that comes from the pump goes to a little gizmo on top of the fuel filter, that is a fuel heater, then the line goes to the tank fron there.
  
  also if you loosend the fuel supply line to the pump, sometimes the copper washers need to be replaced (make sure you did not loose one) or as an alternative to replaceing you can temporaroly coat them with grease lightly.
  
  this next thing i had happen to me on my 89 jetta na. open the trunk and remove everything, remove the carpet, you will see a round black pannel with 3 screws holding it down on the passinger side in front of the spare tire well.  remove that pannel, you will see 2 fuel lines and 2 electric wires. before you touch anything blow that area out with comppresed air, sometimes you gotta break the dirt appart with a screwdriver. now you can check where the plastic line connects, it is connected to a metal pipe, mine rusted through and started to suck the water that likes to sit up there then it sucked air and the car stoped running. but that water seperator holds alot of fuel and i coulda drivin for 20 min on the fuel that is in there. anyway if you want me to post pics of the things to ckeck let me know and hope this helps.
• #2 by dieseltech on 05 May, 2004 07:28
• guess i did not log in on my last post, one other thing to check for, and i know it sucks, but i did have a pump main seal come loose a day or so after replacing (only buy genuine bosch seals) i used some crappy seal that decided somehow shrink and fall out. it sucked air and that was it.
  
  oh BE SURE TO REPLACE THE TIMING BELT IF DIESEL FUEL HAS BEEN IN CONTACT WITH IT!!!.  on my 84 the seal leaked, i changed it the belt "looked" fine  it had ben changed 1,000 miles earlier, well 3 weeks later i got the sickest feeling in my stomach when i heard the noise of a timing belt breaking at 3,000 rpm :oops:  :cry:  so work smarter not harder and do yourself a faver, keep the ol'burner goin.
• #3 by leprechan on 05 May, 2004 13:31
• Thanks for the replies Dieseltech.  I'm running standard diesel, though bio dose sound interesting.  I already checked the sending unit in the trunk and everything looked really good back there.  I made sure to get a new bosch seal for the pump.  I hope I don't have to take the sprocket off again.
  
    When my seal went it sprayed a lot of diesel from the sprocket on the pump and got some diesel on the belt.  I called up napa autoparts and asked them if the belt would be ok and they said they have a special coating on the belts that won't soak up diesel.  They said as long as it didn't get soft it would be fine.  Now I'm not so sure about that.  I definitely don't want to lose the engine.  I cleaned the whole area where the diesel spray was and cleaned the belt, sprockets, and covers.  I'll make sure to give the t-belt a good examination this weekend.  Thanks for the help.
• #4 by leprechan on 05 May, 2004 13:52
• OH btw I've replaced the water pump, thermostat, heater core, and fan thermal switch.  Yet when I go up a long hill the temp gauge still goes all the way up until I"m using little engine power/coasting down the other side.  Could I have some build up in the rad or something.  Bentley talked about the bottom hose collapsing at highway speeds but the hose looked fine when I changed the thermostat.  The system has been flushed and the fluid looked pretty clean.  I curse the previous owner of my car.  It was in tough shape.  I hope I can get it on the road soon.  It will be much more comfortable and it won't cost $40+ to fill the tank.  Thanks in advance for any helpful insight.
• #5 by dieseltech on 06 May, 2004 00:59
• as far as the timing belt having a special coating, i think that may be a line of bull.  not saying it does not exist but i never seen it or heard about it. and i have done hundreds of timing belt jobs, and its also cheap insurance knowing the belt is good.
  
  if you still have not found the leak, you can try this method, it is a bit risky but done carefully you will be fine.  if your air compressor has a pressure regulater on it, turn the pressure down to 5 - 10 psi plug a air gun on and duck tape it into the fuel filler as to pressurize the tank. now go lookin for leaks, but carefull and wear safety gogles or glasses, not too much pressure. you can open the bleed screw on the filter to see if you have enough pressue to push the fuel.
  
  the overheating, well the radiator could be a likely suspect, if you are replaceing get one for a car with a/c, its a tad bigger.
  check your timing with the dial indicator in the end of the fuel injection pump.  no less than .85mm and no more than .110mm if it is too advanced the engine will heat up going up hills.
  
  does the coolant resivior have lots of pressure still in it arter it sits for an hour or so?, this may be a sign of a cracked head :cry:  
  
  good luck
• #6 by dieseltech on 06 May, 2004 01:04
• oh btw i had a 86 td jetta that said it was overheating on hills . turned out to be a bad instrument cluster guage, at the same time i replaced the coolant sender too. been fine for 6 years now.
• #7 by leprechan on 08 May, 2004 23:49
• I finally had some time to work on the car and I think I found my problem.  I can run the engine from a fuel jug with the electric pump, but it doesn't run quite like it should.  At high rpms it kind of starves for fuel.  Also there is only a small dribble of fuel coming out of the return at idle and none when using any throttle.  When hooking all the lines back up to run it from the fuel tank it hardly runs at all.  My electric fuel pump is 4-6 psi and this guy I talked to about it said it should be fine.  I know all my lines are clear and I'm pretty sure there are no leaks.  I also replaced the check valve because it seemed like it was really hard to blow through it.  So I guess my question is, How many psi pump do I need since my vane pump seems to be completely dead?  Thanks in advance for helpful info.
• #8 by dieseltech on 09 May, 2004 11:35
• vane pump went bad......huh. possable when you changed the seal that a pice of it broke off and ended up in the pump? the pump sure went fast after the new seal!!!
  well if that went bad no matter what you do with an electric pump its never going the bo right, the pressure in the pump housing varies a bit with engine rpm, so putting an electric pump would only work for low rpm. when the rpm increases the electric pump still only supplys the same psi.  you said that this is a n/a diesel, any pump from a 86 to 92 would work, the aneroide valve on top of yours and absent on the 85,86,and the 92 eccodiesels. is only there for smoke reduction, i have swapped pumps of 85 on to a 90 and got a bit more power too boot.
  you can use a pump off of a earlier rabbit diesel but it wont have the high idle when you pull out the handle below the ints cluster. it only advances the timing. but it is an option that will work. changing the pump is not bad at all. pumps for the n/a diesel are also a dime a dozen around me, hope the same is true around you.
  
  btw at idle you would only get a dribble out of the return line. the only time the return flows is when your coasting down a hill with no throtle.
  
  anyway good luck keep me posted.
  chris
• #9 by fatmobile on 09 May, 2004 12:36
• This usually isn't a problem but have you pulled the "OUT" bolt and checked to see if the screen is clean.
     I've seen more than a dribble coming out of the return line at idle, when it's running right.
   Did it sit for a long time while you waited to get the shaft seal fixed?
• #10 by leprechan on 09 May, 2004 16:13
• I have yet to check if the screen is clean or not.  Thanks for the suggestion fatmobile.  Also the pump only sat taken apart for 3 days before the new seal went in.  If nothing happens after checking the screen it going to come apart to see if anything is clogged up inside.  Anyone know how much a seal kit costs for this pump?  I have a fealing it going to get rebuilt sooner or later.  Thanks in advance for help on my lemon of a pump.
• #11 by leprechan on 10 May, 2004 23:52
• I found a possible replacement pump for my car, but I'm not sure if it will work or not.  This pump is off an 84 engine and I'm not sure if its a 1.5 or a 1.6.  I haven't had a chance to see it in person yet.  I hope its a 1.6 considering I can get the whole engine for about $100.  Is there any difference between a pump from a 1.5 and a 1.6?  Quick clarification would be great.  Thanks in advance.
• #12 by dieseltech on 11 May, 2004 00:38
• 84 is a 1.6 at least all i have seen were.
  the way you tell a 1.5 pump from a 1.6 is the 1.5 (most of them unless repainted when rebuilt) will have a large yellow dot on the bottom faceing the front of the car on the timing advance piston cover.
   somebody else here may have the part # and know what fits what.
  also the yellow pump uses different timing from all others.
• #13 by Hammy on 30 May, 2004 21:42
• Can a bad pump, or one that has sat for a while cause air to show up in the line? I haven't been able to get rid of the air in my lines either.
  
  Thanks for the great advice guys!
  
  Moonstone (Jason)
• #14 by dieseltech on 31 May, 2004 00:16
• Quote from: "Moonstone"

  Can a bad pump, or one that has sat for a while cause air to show up in the line? I haven't been able to get rid of the air in my lines either.
  
  Thanks for the great advice guys!
  
  Moonstone (Jason)

  
  
  yes a bad pump shaft seal will cause air to get in the lines. sometines the shaft seal wont ever be wet like it is leaking but it will suck air. most every other seal on the pump is under pressure so if they failed you would get a fuel leak, instead of air being sucked in.