85 Diesel Jetta at Wide Open Throttle

[Rolson]

Hi everyone,

I just found this site and have been reading a while. Very informative. I hope you guys can help me out.

The car is an 85 Jetta, 1.6L, NA, 5 speed. Pump was replaced in February 2011 with a remanufactured unit by a mechanic.
Previous owner had the receipt in the file he gave me, along with the old pump for a spare. He never told me why the pump needed to be replaced. It has only been driven about 6-7,000 miles since the pump was installed.

The other day as I was going down the road at 55 mph, I came to a 45 zone, took my foot off the throttle and no response. Rpms stayed high. I tried to lift the pedal with my foot, and it was already up. I pushed in the clutch to slow down and pull off to the shoulder and the engine went to WOT with no load. HUGE cloud of smoke behind me. I immediately shut it down. Opened the hood and everything looked normal as to the throttle cable and linkage. It is in the idle position and the springs have full tension on them.

Later I towed it home, and decided to attempt to start it. Immediately went to WOT, so I shut it down again.

I cannot see anything wrong from the exterior, so I am assuming there is some type of internal spring that is broken and I need to replace it, but have no experience with these Bosch VE pumps. I have seen the blow-up diagram of the pump parts from VEXEL this morning, but cannot find much to identify which spring might be at fault. I don't know that it is a spring, That's an assumption on my part.

Can any of you experienced elders tell me what to look for and if I can do the repair with the pump on the car or do I need to remove it first?

Thanks for the help!!

Rick

[CarlosA]

I think the consensus will be that you had diesel "runaway", rather than a injection pump problem.

http://www.youtube.com/watch?v=5zx3qKX_Pno

[82vdub]

Although, if it shut off with the key without much fuss and fairly quickly, it's not runaway.

[EcoTX]

Hello Rick, glad to try and help another fellow VW IDI diesel lover.

I'm not an elder by any stretch of the imagination, but I can give you a few things to check out and maybe determine if something internally is wrong or not.

The only two things externally on the pump that control the fueling are the throttle shaft position and the max fuel screw.

1. Check that the max fuel screw is set right and tight (if it is screwed in too much, you will have hanging RPM's and/or instant high revving on startup much like you describe)
2. Check that the throttle shaft splines aren't worn (in this case the throttle linkage would move independently of the throttle shaft in the center)

Number 1 isn't all that likely, since if the locknut was loose, the screw would probably have been backing itself out over the last 6-7k miles and you would have the opposite symptoms, but it won't hurt to check. Check if the screw still has the metal "collar" in place and the 13mm locknut is nice and tight.

Number 2 is more likely because the splines / teeth on the shaft are very tiny, and if they are not lined up right and someone FORCED tightened all the throttle assembly down on it, it would have held for awhile but now may have worn so bad from vibration / etc that the throttle linkage isn't turning the throttle shaft anymore. Still this is a stretch, but something to definitely check before taking the top off the pump and checking springs.

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OK here's the pics. This pump isn't exactly the same as yours, but it is similar enough to check what you need to I think.

Max fuel screw, if the metal collar is still on it I would rule this out as being the issue since it is there to prevent being screwed in too much.
Also if you have the collar in place, I wouldn't hesitate to take a 13mm and loosen that screw out a ways and see how it acts when you crank it up.
It should eventually prevent it from starting at all the more you screw it out.
This would in fact narrow it down to a pump / fuel issue so I highly suggest you try it first.



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Top of the throttle shaft with throttle linkage still in place.
All of the pumps I've taken apart, removing that nut and little lock washer hasn't sent the throttle linkage flying off, but it technically is the only thing holding the linkage on the shaft so be aware of that. I usually have to wiggle and fight with it to come off actually. You could just loosen the nut a little bit, and try turning the shaft with a small flathead in the slot on the top. That shaft should NOT move independently of the throttle linkage. If your splines were worn that bad, and the shaft jumped some teeth and got "stuck" in the mid-upper throttle range I'd imagine you could turn it independently of the linkage. If you can, you found your problem.



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Throttle linkage removed with top portion of throttle shaft showing the tiny splines that grab the throttle linkage.



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Try these things and get back to us on any results. Don't be intimidated by possibly needing to take the top off the pump, there really isn't much in these rotary pumps and taking the top off is very easy especially if you have one of the earlier pumps. Plus you're in good hands here on the internet, lots of knowledgeable people and tons of information at a few different forums that cater to these old VW diesels.

[Fatmobile]

Hello Rick, glad to try and help another fellow VW IDI diesel lover.

I'm not an elder by any stretch of the imagination, but I can give you a few things to check out and maybe determine if something internally is wrong or not.

The only two things externally on the pump that control the fueling are the throttle shaft position and the max fuel screw.

1. Check that the max fuel screw is set right and tight (if it is screwed in too much, you will have hanging RPM's and/or instant high revving on startup much like you describe)
2. Check that the throttle shaft splines aren't worn (in this case the throttle linkage would move independently of the throttle shaft in the center)

Number 1 isn't all that likely, since if the locknut was loose, the screw would probably have been backing itself out over the last 6-7k miles and you would have the opposite symptoms, but it won't hurt to check. Check if the screw still has the metal "collar" in place and the 13mm locknut is nice and tight. (Picture of screw and locknut coming later)

Number 2 is more likely because the splines / teeth on the shaft are very tiny, and if they are not lined up right and someone FORCED tightened all the throttle assembly down on it, it would have held for awhile but now may have worn so bad from vibration / etc that the throttle linkage isn't turning the throttle shaft anymore. Still this is a stretch, but something to definitely check before taking the top off the pump and checking springs (Pic coming later).

I will update with some pictures of all this and some more info when I get off work in a few hours...I ran out of time here on my lunch break!

Hey,.. that new guy's pretty good.
You'll probably end up pulling the top off the pump but a good list of external things to check,..
also check the idle stop screw,.. sometimes the locknut is loose and it vibrates inward while the driving,..
when the arm isn't against it.

[CarlosA]

Although, if it shut off with the key without much fuss and fairly quickly, it's not runaway.

I totally missed that detail, lol.

[Rolson]

Thanks everyone for your replies.

Here is an update.

Today I did find a Bosch book with detailed online diagrams which were pretty helpful also. After looking at the diagrams, and the other website of a Bosch pump rebuild/reseal with over 100 photos, I felt pretty confident I could take the top off and look inside. I was hoping it was something simple like a broken governor spring.

I have an old pump like the ones in the pics above, that the PO put in a box. I decided to take that one apart first.

Once inside I saw what a good governor spring assembly is supposed to look like.

Next, I took apart the top of the pump on the car. I did check the various adjustment screws as suggested. All the locking nuts are tight. Nothing wrong there.

The splines/teeth on the top of the shaft are good. No slippage or worn teeth there to cause a problem.

I proceeded to pull the top off the governor assembly to see if the spring was broken. Everything looks good there also.

At that point I decided to re-assemble the top portion of the pump and call it a day. I will wait until I can spend a whole day to completely dis-assemble the entire pump to find the problem. It must be deeper in the pump I guess.

It did immediately shut down both times with the key so I do not think it is a runaway situation.

After I re-assembled everything today, I attempted to start it several times just for grins to see if it repeated. No luck.

Maybe I did not get all of the air purged out after the replacement of the top cap. I thought I did though.

Thanks again everybody for your input. Any other thoughts? I'm open to suggestions.

Have a great Independence Day!!

Rick

[Fatmobile]

I had this happen to me once,.. in an '85 Jetta TD.
When I pulled the top off I saw the flyweights were stuck,.. the one I was working on had sat for quite awhile,.. not some sudden problem while going down the road.

[Rolson]

Here is an update of what I have learned in the last 2 days.

Diesel Dean,

Thanks for the emails and pointers in the direction of runaway. I wish I could say that is the case here, after today I cannot.

I read for a couple hours on here today of others descriptions of their runaway experiences. While at first glance it does seem similar, it seems a little different to me. Please correct me if I am wrong.

In my reading, I found that several of the forum members that had that experience were able to shortly start the diesel again and it worked fine. The oil was either cleaned out of the filter box, or they put in a catch can to prevent the oil from getting to the intake any more.

Hoping that would be the case, today I looked at my Jetta very closely. First, I noticed that the breather line comes off the top of the valve cover and tees, then feeds into 2 ports below the air box, directly behind the head. The air filter box was completely dry, as it should have been. Next I did look down the hose barb on the valve cover and there is a splash guard in there to prevent oil from getting sloshed up the hose. Third, I was able to start the car twice and each time it immediately revved up to WOT, and I shut it down with the key. As I understand it, if it is runaway and burning the oil, the key will not stop the engine.

So, it still looks to me like it is an IP problem. I have removed the top of the pump to check the governor spring, hoping it would be broken, as that would be easy to fix. Unfortunately, that was in perfect condition.

I believe it is a spring located deeper in the IP, but I have never taken one apart so I do not have any idea what a good IP looks like inside, other than the excellent photos I found here last week of the re-assembly of an IP that I can follow.

Anybody willing to chime in their $.02 with this new information?

Thanks.

Rick

[82vdub]

If the key kills it, it's not runaway.

[CarlosA]

If the key kills it, it's not runaway.

I kinda wondered if it might be a mix - not quite enough oil to run away but enough to make the engine race. I don`t have any experience here.

[Diesel Dean]

It sounds like you are on the right track, If anyone can help you find the problem the guys on here will. I know I said my bet was on bad rings but like 82vdub said if you can still turn the car off with the key it's not bad rings. It may after all be your IP.

[Rolson]

Ok, so the consensus seems to be that it's not runaway.

With the right knowledge and photos, and detailed directions I believe I can take this pump apart and find the problem, and locate replacement parts. I might have a good part inside my spare pump in my shop.

Anybody care to chime in about a good rebuilder, or place where I saw those photos of the guy who replaced the seals and then put it all back together? I found it somewhere on the web last week, but did not bookmark it.

If I do take it apart, what should I be looking for? Broken or collapsed spring, or something else? I know the tolerances in these pumps are very tight, is it possible it just has a grain of sand or something hanging it up inside? Any thoughts?

Thank you to everyone who has spoken up so far. I appreciate your time and experience being shared with me.

Rick

[CarlosA]

Rebuild thread is on this site.

viewtopic.php?f=8&t=6694

[Rolson]

Thanks CarlosA!!