Getting a '90 Jetta running better

[sundogfarmer]

I just bought a barely running 1990 1.6 L Jetta (n/a, 314k km) that has a veggie oil conversion installed. I'm hoping I can get it running well enough to use for trips when I don't need my truck. The guy I bought it from tells me it was running well but that it had a leaky IP. He then had a shop swap the IP from another running Jetta he had and since then it has run right. Here are the problems:

Hard to start - got to give it lots of gas to get it to start and keep gas on to keep it running for a while

Noisy - are these engines usually so loud? I have a Cummins too and I think this VW is pretty loud.

Once it's warm, you can leave it in park or neutral w/o extra gas but if you shift into gear without giving it gas it'll stall.

It doesn't stall quite so easily when the choke is pulled out.

There is air in the fuel lines for the diesel fuel tank (seen in clear plastic tubing). But the problems persist (only slightly improved) when I switch over to veggie oil, which does not have any bubbles in it.

Definite lack of power

I made the mistake of taking it onto the highway... after a few miles at 75 km/h the oil light came on. When I pulled over and looked under the hood there was oil coming out of a weep hole on the engine block (kind of whistling/hissing) in the area below the #3/#4 injectors. This hole has not been weeping since when it's running. Is this some sort of relief valve or did I cook this thing within 15 minutes of getting it? The temp gauge never got very high, but I have no idea if that works properly either. It never got up above the 2nd mark.

I've messed around with the timing today (no dial gauge, just marking and turning it) but I can't make a decision either way. It being so noisy tells me it's advanced, but the fact that it idles better with the cold start out tells me it wants to be more advanced. But when I retarded it a bit I think it ran a bit better. When I advanced it I had even more difficulty getting it moving in gear. So I basically have no idea.

Think I'd like to hear some theories out there. Ready set go! Thanks!

[ad]

First off, you need to get rid of the air in the lines. It will never run right with air coming in. Occasional large bubbles are ok, but foamy soap bubble looking stuff will not run right.
Hard to start often = air in pump
Since there is a veggie kit installed, my guess is that it is sucking air. Veg kits will have lots of T's in the fuel lines and spliced hoses, switching valves, separate filter, etc. each one could be a potential air leak.
Next, if you have the OEM style fuel filter, the recirculation valve sometimes is a problem. If you get one of the older style filters for a rabbit, it will eliminate that possibility.
I would suggest disconnecting all the veg lines and get it running straight from the diesel filter like it was intended first. Once you get it running properly on diesel, then you go back to veg if you desire. If you cant get it to run right on diesel, the veg only complicates matters.
Next: A diesel with automatic tranny?...I didnt know they existed, I think the vanagons may have had them, but never seen it in a jetta. Was this an engine swap? God that thing must be slow.

WEEP HOLE IN THE BLOCK ?!?!
Aint no such thing, all that comes to mind is the vacuum pump and the block off plate, maybe the base of the dipstick tube? Whatever hole you mean, it seems like you had excess oil pressure. Could be combustion pressure or oil pressure. Please show a pic of this "weep hole"

VW's are not that loud, my guess is your timing is off and/or sloppy injectors, both of which can make it sound really rattly and annoying.

[82vdub]

I would suggest eliminating the air in the lines like ad suggested. One way to troubleshoot running issues is to rig up a jar of fuel that's elevated above the IP with an inline filter and see how it runs. However, it doesn't seem like you have a fuel supply issue, possibly a delivery issue and timing issue.

But, start with the air in the lines first. Next, if you don't have a Bentley repair manual, get one. I'd then proceed to set the base timing according to the Bentley so you at least know where you're at, and then play around with it from there. It's possible that the IP is just worn out and it won't run well without a rebuilt IP.

Is there any smoke coming out of the back when it runs? White is a sign of poor combustion. You may also want to check the compression of the cylinders, as low compression can cause poor combustion as well.

[sundogfarmer]

Hi,
Thanks for the help! I got a Bentley manual with the car but for troubleshooting like this I much prefer (and learn a lot more from) having people bounce ideas around.

The air in the lines might be a bit more than I have time to deal with at the moment. It's not foamy but large bubbles, about 1 bubble/sec. The guy I bought it from said that he had all the fuel lines replaced when he noticed the air and that didn't help. He thought it was something in the tank, like the pick-up straw. When I get some fuel I'll top the tank up and see if that helps. I checked where the lines go into the veggie oil fittings and they seem pretty good. When it's running off veggie oil there are no bubbles. But I'll pick up some fittings so I can try bypassing the veggie oil valve to see what happens. That'll be tops on my list once I get what I suspect is the timing issue resolved, because it is definitely a major contributor to the hard starting.

There was white smoke when I advanced it yesterday. Not any after I retarded it again, except at start-up.

For timing I don't have a dial gauge so I'm doing it by trial and error. My latest trial/error was to retard it more than I did before (~1/8") since advancing had made it run even worse. And it was better. After it warmed up enough to go to veggie oil, I could actually shift into R or D (agreed that auto in a diesel is dumb... but I take what I can get for pennies) without it stalling. The engine didn't sound too happy about it, like it was ALMOST stalling, but it stayed running. The weird part is it ran almost like it should when I pulled the cold start out. I could sit in D with my foot on the brake and it idled happily. So this is confusing... on one hand retarding it at the IP makes it run better than advancing but, but advancing via the cold start makes it run even better. I can't quite wrap my brain around this.

I know the cold start advances the IP 5 degrees. Does it do anything else that could account for this? How many degrees does 1/8" rotation of the IP correspond to? Could I be sitting in between proper settings and I need to jump the belt a tooth or something?

To advance the timing I am pushing the top of the IP towards the head. To retard it, I'm pulling the top of the IP towards the front of the car. I'm 99.9999% sure I've got that correct but given the nature of this problem that's where the .0001 comes in.

[sundogfarmer]

It's located underneath the #3 and #4 injectors, under the radiator hose. The yellow wires go to the oil filter.


http://imgur.com/h0HRaRu

[Fatmobile]

That's what I was afraid of.
Not a weap hole. Probably a head gasket.
The oil pressure runs from the block to the head right there.

Expect white smoke with air in the fuel.

Probably a clogged in-tank screen,.. probably got some vegy in the diesel tank.
Air in the fuel is almost always a fuel line restriction. New filter might solve it.
Get rid of the water seperator under the car if it's still there, along with the check valve.
Disconnect the fuel line at the water seperator and the tank will drain/syphen dry, on you.

[82vdub]

To advance the timing I am pushing the top of the IP towards the head. To retard it, I'm pulling the top of the IP towards the front of the car.

That is correct. It's odd that is smokes more when you advance it and less when you retard it. Engine should be really loud when it's too far advanced, which goes back to your base question and my question on setting the static timing yourself. If you're starting from what someone else did, it may be so advanced that you retarding it is getting it to run better, but to know for sure, set the static timing yourself first.

To troubleshoot your running condition, I would bypass all the fuel system to a good known source (no air) and then troubleshoot it from there. No sense trying to troubleshoot an entire fuel system, possibly timing issue, possibly low compression and possible shot IP if you can't eliminate something from this list. You can spend hours trying to troubleshoot it all until you eliminate something somewhere.

[Caerbannog]

I'm a little late to the party, but RE: the oil leak, I had a similar situation here: viewtopic.php?f=8&t=11353
It killed me that it was running well to have to change the head gasket, but there you have it. Plus I was losing almost a quart of oil every tankful, and having to carry a piece of cardboard to everywhere I parked was a little embarrassing! And you know how messy that diesel oil can be.

I used copper spray on my HG, and fingers crossed, two years later, we're still dry.

[sundogfarmer]

Thanks for the HG info
. I think i do have to replace it as there is an oil film on the surface in the coolant res.

I messed around with the fuel system today. Took out the fuel sender and just hooked the fuel line up to a jerrycan. Ran fine, very few bubbles. I noticed the return line was pretty frothy. Could the return line ne causing this? The fuel sender seems ok, i was able to siphon fuel through it.

[sundogfarmer]

I hooked up a clear line on the return line between my IP and WVO/diesel valve. It was extremely frothy. Are the braided return lines between injectors usually clamped on?

[TylerDurden]

Frothy return is usually from air inside the IP... it's like a blender in there with all the parts spinning and then the overflow gets pushed out a pinhole into the return line.

The injector bleeds usually do not have clamps, the pressure is very slight. they will weep when running and may let in air when sitting.

[Fatmobile]

Right the return line is under slight pressure.
No air going in and foam coming out is usually air getting pulled past the mainshaft seal.

[Quantum-man]

Are you running veggie oil, or biodiesel?
Are you shutting down engine with non diesel in the pump? Maybe this is your issue?

[sundogfarmer]

Yup, I know to run it on diesel for a while before shutting down after using the veggie oil.

I just spent a couple hours messing around with the fuel tank. I took out the sender unit and plunked it in a clear jug full of biodiesel and played around to see what gave bubbles and what didn't. The return line into the sender wasn't as bubbly after non-aerated fuel had run to the engine for a while. But there was always at least a little bit of air. Anyway, it didn't seem to necessarily cause bubbles in the fuel going to the engine since I could get it running nice and smooth through the sender with no bubbles coming out. What DID seem to cause problems was what appears to be a fuel pump. When the wire connector on the sender was unplugged it ran w/o bubbles, but plugging it in caused bubbles to start coming out in the fuel.

In-tank fuel pump? Yeah... these diesels aren't supposed to have one, right? But it's got a 4 wire connector and 2 of them go to a little round unit at the bottom of the sender. It doesn't seem to actually pump. If I disconnect the line to have it draw out of another container it doesn't squirt fuel out or anything.

Anyway, just unplugging it doesn't solve everything as the unit doesn't seem to reprime itself very well. It just sends bubbly fuel until I reprime the line by disconnecting it and sticking it directly in the jug. At which point I can reconnect it and it sends a good flow.

I haven't been able to find any replacement sender units. I think I might be able to just remove the pump and stick a hose in its place, though. Has anyone just done a simple straw/hose and strainer type setup on these?

[Fatmobile]

Sounds like you have a gasser to diesel conversion.
Not sure why disconnecting it would make it flow easier.