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Leaking diesel injection pump

18603 Views 5 Replies 4 Participants Last post by  myql
Hi there and Merry X-mas to everyone! I'm a new member and had a bit of a struggle finding old discussions on the topic that interests me. So, I'll start a new thread.

I have a Golf diesel and its fuel injection pump has developed a leak. I didn't notice it at first, but realized that my fuel consumption had increased, A few days ago, while waiting for the green light at an intersection, my engine stalled, but I managed to start the car. Later that day, the engine attempted to stall again a couple of times on idle speed (at traffic lights), and every time, I kept it running by pressing on the gas and revving it up. After I came home, I decided to run the engine on idle again to see if it stalls. It did. So, I rolled up my sleeves and soon figured the cause - a plugged fuel filter. Draining it didn't do the trick, and the engine continued to stall on the idle speed.

Then I filled a 3L plastic jug from corn oil with a clean filtered diesel fuel, secured the jug inside the engine compartment (to make sure that it doesn't get damaged by the alternator belt or pulley), disconnected the fuel line at the filter (pump suction) extending it by appr. 1-1.5 ft, and put the free end of the line inside the jug. The engine started like a charm.

I hopped in and drove to the auto parts store to pick up a new fuel filter. The return trip was no more than 16 km (or 10 mi), and I figured that I should have about half of the fuel left in the jug when I get home. But somewhere in the middle, the engine stalled again. Completely puzzled at this point, I popped the hood to check the fuel supply, and much to my surprise found the empty jug. The reason was quickly found: in a hurry to get to the parts store to pick up the fuel filter, I forgot that the return fuel line was still connected to the main tank and all excess fuel returned there. I filled the jug again with the clean fuel (which I had plenty in the gas can) and the rest of the driving was OK. When came home, I checked the fuel level in the jug again - it was appr. 1/2 full. I expected it to be 2/3 full, and it crossed my mind then that I had an unusually high fuel consumption, which I couldn't explain.

In a couple of days, when the weather was dry and sunny, I went outside to work on my car. I replaced the filter, filled it with fuel and connected the jug to the injection pump, but this time, via the filter. My numerous attempts to start the engine were unsuccessful, and after many tries I discharged the battery so the engine won't turn. I charged it overnight and tried to start the engine next day, but no luck.

The stop solenoid on the pump was OK: the voltage was 12.8 V and the solenoid produced a slight clicking sound when I disconnected the wire and touched the stud on top of the solenoid a few times (both tests were done with the key turned "to pre-ignition").

Next, I pulled all injectors, and while they were out, checked the glow plugs. All 4 were OK. The compression test was next, and it didn't cause any concerns: all readings were at an acceptable level and the difference between 2 adjacent cylinders was within a normal range. I didn't do a leak down test, but decided to check the injectors for spray pattern. I connected 1 injector and placed it inside a glass jar to catch the fuel, while other 3 unions on the discharge side of the injection pump were not connected to anything, and arranged to catch any fuel discharge from these unions and direct it into a tin can that I placed under the injection pump. From inside the car and through an opening below the hood, I could see the glass jar with the injector inside connected to the pump.

However, that's when I was really surprised: cranking the engine didn't produce a single drop of fuel discharged from neither the injector nor from any of the 3 unions that were open. I thought maybe the line was filled with air and decided to step up the test: by-passing the filter, connect the fuel injection pump suction to the funnel, fill it with the fuel and raise it to appr. 1.5-2 ft above the pump. Having done this, I turned the engine again trying to obtain a spray at the nozzle of the fuel injector or the unions. This didn't happen, and when I stepped outside of the car, I noticed that the fuel level in the funnel and clear plastic tube was dropping steadily and quickly. That was unusual, and I looked under the car. Sure enough, the fuel was dripping on the pavement from the bottom.

At this point, the fuel pump had become the main suspect, but even having removed the timing belt cover, I couldn't see where the fuel was leaking from: it could be through the main drive shaft seal or through the cold start lever seal.

This could explain the increased fuel consumption that I had noticed. But why even with the leaking seals I couldn't get the engine started or get a spray at the fuel injector nozzle during the test?

Is this because not only does the fuel leak out through the faulty seal(s), but also the air gets in, and starting the engine becomes a problem, especially in the morning?

Also, I read somewhere that leaks similar to mine could be caused by switching from a pure biodiesel to a reg. diesel. This was my case, and during a major part of 2009, I used pure biodiesel. When my supply ended, I switched to reg. diesel which I bough in Canada or the US. I knew that biodiesel caused seal and O-rings to swell, but didn't realize that a switch back to a reg. diesel fuel - which is now produced with a very low sulfur content (or ULSD) - causes the opposite effect, shrinking the seals and O-rings.

Overhauling the pump or replacing the seals - only because they leak (and that leak is caused by switching to ULSD) - is a very expensive proposition as it could cost from $320 to $800 for tested pumps (with core), or around $200 - 250 for untested (and not guarantied). By comparison, a new seal kit for my pump could be around $20-30.

I'm up to the challenge and have the ability and knowledge how to replace the seals, but I'd rather avoid this because fiddling with the fuel pump is always tricky.

Has anyone of you, fellows, experienced the kind of a leak I described? Would a simple switch to pure biodiesel (or B80-90 blend) cure the problem?

I appreciate any advice and opinion on the subject.

Merry X-mas and Happy New Year again!
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Same here > Leaking FIP

I'm going through similar. FIP ( Fuel injection pump) Started leaking after the 100k service ( $800!)
My TdiForum post here:

I'm going to try to re-seal ON-CAR, but don't have a VAG-COM.

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