inj pump runaway - Troubleshooting - VWDiesel.net The IDI, TDI, and mTDI source.

• inj pump runaway by jari_veedub on 12 Aug, 2007 07:14
• I just replaced my bosch pump with an identical one from the auto wrecker.  It's a 93 golf 1.9L IDI.  I've replaced a few pumps  in the past in my other cars, and this one is really no different.  I set the plunger timing with my gauge tool and all should be normal.  When I start up the engine, it starts good, but within 2 seconds the engine runs away on me.  I shut it down immediately before it self destructs.  All the screw settings are identical to my original pump.  I backed off the throttle screw to the farthest low, and the engine still does the same thing.  
  I searched "runaway" on this forum but didn't find anything specific to this problem.  I suspect a bad pump.
  Any help would be much appreciated.
• #1 by Zulfiqar on 12 Aug, 2007 09:28
• the screw stopping the fuel increase lever is the residual fuel screw. The idle screw is located behind the pump, I think that your advancing mechanism is stuck or gelled up.
  
  So when it runs away - does it make a black cloud?
• #2 by Peter on 12 Aug, 2007 13:26
• it could be as simple as having "air" in the system...several yrs ago I had opened up the fuel system in Mexico ( fuel line exchanged ) and it raced like it would blow, then quite again and it did this for what felt like a long time, especially when people were looking at you while you are waiting for the light to turn green,, maybe 10min. of driving took care of the problem
• #3 by Peter on 12 Aug, 2007 13:27
• it could be as simple as having "air" in the system...several yrs ago I had opened up the fuel system in Mexico ( fuel line exchanged ) and it raced like it would blow, then quite again and it did this for what felt like a long time, especially when people were looking at you while you are waiting for the light to turn green,, maybe 10min. of driving took care of the problem
• #4 by jari_veedub on 12 Aug, 2007 20:40
• I'll check the idle screw behind the pump.  I guess that screw is the one with the fuel advance rod attached to it.   The advance mechanism is at the normal driving position.  I compared everything with the pump in the car and the pump I just replaced.  They're identical pumps.  
  When I start it up, I can only let it run for 2 seconds because she'll blow up otherwise.  When it does start up it seems to make the typical diesel exhaust smoke.  It doesn't seem to be all that black.  Normal sticky "good smelling" diesel exhaust.
  I've changed out these type of pumps in my previous veedub diesels and have never encountered this type of problem.  I sure hope it's a simple fix because it's a lot of work changing out the pump.
  What's a good manual for this bosch pump?  The original bosch manual?  If anyone has an ISBN # or the name of a good manual, I would like to pick one up and keep it on hand for reference.
  
• #5 by jari_veedub on 13 Aug, 2007 05:08
• I started up the engine again this morning, and in regards to smoke, it is quite black.  And... again, it started up as a normal diesel, but within a few seconds, it totally races away on me...
• #6 by QuickTD on 13 Aug, 2007 06:36
• The governor linkage in the pump could be sticking, particularly if the replacement pump has been sitting around.
  
   On AAZ pumps it is possible to manually cycle the governor linkage to free it up. If you look at the front of the pump, just below the accelerator cable bracket you will see a small lever. On cars with automatic transmissions this lever has an arm attached and is used as an emergency stop. It manually pulls the governor to zero fuel to stop the engine. With the engine off you can hold the throttle lever fully open and cycle this emergency stop lever to help free up the stuck linkage.
• #7 by jari_veedub on 13 Aug, 2007 16:36
• I tried cycling the lever under the throttle bracket to reset the governor, and it didn't do a thing.  The engine still over revs when I start it up.
  I think I have a bad pump.
  
  I am going to replace the seal on the main shaft.   I should be able to do it without tearing the whole pump apart.  Can anyone tell me if I can replace the seal on the fuel advance shaft without too much teardown?
  
  I am for sure going to start using an additive for the low sulfur fuel these days.  This is the 3rd pump I've tried to replace because of leaky seals.  Any good additives other than 2 cycle engine oil?  I heard the low sulfur fuel doesn't have the aromats or whatever it's called to keep the seals swelled up.
  
  Not sure what else to try and trouble shoot
• #8 by jari_veedub on 20 Aug, 2007 06:21
• I got another inj pump from the scrap yard and put it in the car last night.  Tried starting up the engine and it wouldn't start, kick or anything.  The fuel solenoid does make a make a click sound and appears to work.  I am getting 12v to the solenoid.  Glow plugs work and were replaced, fuse is good.  I set the plunger timing with my dial gauge tool.  I was going to crack a fuel inj line to see if it's trying to push fuel through... but,
  It was late last night, so I gave up and went to bed.  Frustrated.
• #9 by Slave2School on 20 Aug, 2007 08:35
• They sure dont' like air.  If you have a vac pump suck fuel out of the pump return line till you get a steady stream with no air, it might save you some frustration.  I had to do that the last time I changed a fuel filter since I forgot to prefill it with the inline pump..oops!
• #10 by jari_veedub on 20 Aug, 2007 08:38
• yeah, I should have mentioned that too.  I used my vac pump to get the fuel going.
  I am going to crack the line and try again when I get home from work...
   :?
• #11 by saurkraut on 20 Aug, 2007 12:56
• I suspect that the vane pumps get sticky in these things after they sit a while.  I have had success by "pushing" fuel through the filter and into the pump, where the suction method failed.  Get an outboad motor type in-line primer bulb an push it through the filter.  Worked for me once...
• #12 by jari_veedub on 21 Aug, 2007 05:23
• Last night I went through all the obvious things I can think of.  I primed the fuel pump again, so more air came out, glow plugs function ok, shut-off solenoid sounded like it worked, all the screw settings on the pump were identical to my original pump, fuel advance mechanism appeared ok.
  
  I cracked one fuel line to see if fuel was getting to the injectors.  It was dry.  However, after what seemed like an hour, the pump all of a sudden started to push fuel through the injectors.  I tightened everything up and got 'er running.  I assume the pump was sitting for a while and something was stuck internally.  I've never had this much problem with these style of pumps.
  
  I took the car for a test drive (about 25 km distance) and got it normal op temperature. However at idle there seems to be a miss/skip.  Somewhat of a rough idle.  Maybe after driving it some more, it will clear up.  The plunger timing is at 0.033".  
  Any comments?
  Thanks again for all the feedback.
• #13 by Slave2School on 21 Aug, 2007 06:30
• You could try to run a can of diesel purge through that puppy to see if that will clean up any gunk left in the system, might to do something, might not.
• #14 by jari_veedub on 21 Aug, 2007 10:55
• I took the car out for another test drive and the car seems to run good.  It's somewhat lacking in power at the lower rpm's but not that bad.
  
  Filled the tank with fresh fuel and I added some Kleenflo low sulphur diesel additive.  Is this a good product or does anyone recommend something better for diesel lubricity.  I read on this forum that stanadyne is good, but expensive though.  Also 2cycle oil.  ?