Starting problem, (NOT a glow problem)

[killerrabbit]

I am a professional diesel mechanic, and even I'm getting stumped.

I have lurked about on a few VW forums, and everybody is quick to blame the glow plugs. well, Mine work and I know it, because I tested each one, and hard wired them to a heavy solenoid and a switch on the dash.

That being said, Ive got two giving me fits.the first one is my wife's 81 rabbit with a 1.6lNA Diesel just flat out will not start. I thought it was a cold issue, since its been getting into the teens, but now Im convinced its something else. At first it wouldn't start unless plugged in for an hour, or had been running within the last 4 hours, (after that I had to plug it in). until yesterday. I plugged it in at work and still had a hard time starting it in the morning, then drove to an appointment that only took an hour and a half, and then nothing, not even smoke out the tail, it just cranks and cranks and cranks, the engine was even still warm to the touch. I went straight for the fuel solenoid, and got power there, so I pulled the guts out thinking it was stuck or something. after an hour of trying to jump it, we finally pull started it, and it took forever for it to finally start, and #4 was misfiring. I limped it away and installed an old injector and the miss went away. then it sat in 16 degrees for 2 hours, and would not start again, same as before, not even a puff of smoke or an attempt to fire. I finally destroyed the starter trying to start it. If I give it a looong hill to roll start, or pull it with another vehicle it will eventually start, but even then it takes a good 30-40 feet with the motor turning before it will.

As I said before, Im a Pro, I work on semi tricks for a living, so all the basics have been ruled out, (filters, air in fuel, glow plugs etc, and unless something came unbolted, all the timing is spot on) I have a theory, and I believe I not only have weak injectors with 189,000 miles, but possibly a worn rotor in the pump, and those combined with the cold weather is making it almost impossible to start. I don't have the tool anymore to check internal pump PSI, but it does have good steady flow out the outlet when cranking. I suppose I could rig up a gauge to an old banjo fitting.

the second was my brother in laws 84 golf, with a transplanted 1.5lNA diesel out of a 79 dasher, was doing something similar, until I readjusted his cam timing, wont know till tomorrow. when he tries to start it in the cold.

if you have any other theories, let me know., and is 100 psi oil pressure normal at 2500 rpm hot?

[82vdub]

Well, typically if you plug it in and it starts and when you don't it doesn't, that's a sign that it's glowplugs. That's an easy way to test whether they are working or not, without much effort.

However, are you sure you don't have a fuel blockage and the fuel is siphoning back to the tank? This has happened many times with others, where it's plane hard to start hot or cold. If you can rig up a vacuum gauge on the inlet of the IP, this will tell you if you have a blockage in the fuel system if the vacuum gauge gets too high.

[TylerDurden]

I'd check the compression... under 250 and they really don't want to start in the cold.

[Prairieview]

Well, the pro's I know would (as above) question compression and valve clearances.

[ad]

Put a clear fuel line on the input and output of the pump so you can see if there is air trapped in there.
Do a compression test.

Both air and low compression could cause the symptoms you describe.

Also, since you're a pro you should be able to take your injectors to work and pop test them, clean, and adjust, no?

[killerrabbit]

Well, I would love to do the pop test, but where I work, this stuff is so obsolete we dont have the equipment anymore, I think it might be worth the investment if I could find a good used setup, but they are gettin kinda rare and pricey, suppose a visit to ebay is in order.

As for compression, Im actually trying to avoid that scary venture, Ill consider it at last resort, I should have been more clear, it ran fine untill last week, even started ok in the cold. it gradually got harder and harder to start over the week, but didnt get any colder. and my wife says it did it only once to her about three weeks ago when it was still in the 60's, so I doubt it lost compression that quickly, its almost got 200k on it so Im sure its a bit lower these days, and as before, this stuffs so old I dont have acess to that stuff anymore, but if I have to I know where I can borrow a compression test adapter.

Im rebuilding the pump that came on it (ran perfectly, but leaked badly out of the cold start lever) swapped the one thats on it now after a seal kit, had some wear on the rollers but everything else seemed fine, I wonder if the rollers are getting chewed and the bits are tearing everything else up.
the old pumps apart and the rollers and plunger are perfect, I dont think it had many miles on it, but sat so long the seals dried up. I got a set of new rollers and a 1.9l camplate anyways. I do have clear line, the rubber stuff from the parts store, even though it says its diesel rated, still rots on me. I stuck on some vinyl clear stuff on monday because I thought air was my problem. now if it sits a while and I crank it, there are a couple little bubbles that zip through out of the filter but thats it, as fast as they are moving I almost wonder if the regulator is stuck open.

I just ordered 4 new injectors, and they are merc rated ones for biodiesel and veggie oil, since we are setting up a veggie oil refinery i figured they were worth it.
the old injectors have some pretty deep wear on the nozzle so Im pretty sure they are at least part of my problem. I bet on the pop test they dribble, or at least dont have a good pattern anymore. (Im told this motor can go as far as 500k if cared for, how long do injectors last I wonder? 200k seems about right)

the main reason I suspect the pump is the way it just cranked and cranked and cranked before I even would get smoke, then a bit of sputter, and finally it would start, but it got worse and worse untill the battery just couldnt crank it long enough.

Im gonna stick in a rebuilt pump, and stick in the new injectors and see what happens, if I still have trouble Ill gather the stuff to do a compression test. and Ill check my valve clearence once the valve cover is off, I dont have a shim kit, but I do have three heads, one dropped a valve and the other 2 are cracked, should be able to scrounge up thinner shims if need be, and it probobly wouldnt hurt to replace the valve seals while Im at it.

[TylerDurden]

Even bad spray will get puffs of smoke, provided the air in the cylinders gets hot enough by compression.

Why would towing/pushing start a motor with low compression?... a fast spin of the crank gets the air in the chambers hot enough before it gets a chance to leak down past the rings. Towing also repeats the fast crank enough to warm the cylinders.

I have been there... killed starters, re-sealed IPs, pop tested injectors, added block heaters... compression is fundamental and easy enough to check. Maybe the FLAPS (Friendly Local Auto Parts Store) has a test kit they loan.

Pop testers are easy enough to make from a bottle jack. But again, even crappy spray will run a motor (poorly).

A messy but effective way to validate fueling, is to put the lines and injectors on the IP so they spray into the air (injectors not in head); crank a few seconds and clean up. No spraying at all might be a simple bad connection at the fuel cutoff solenoid.

If injectors are spraying, then it is down to timing and compression.

Another easy test... blast a heat-gun into the air intake when cranking (like a Cummins grid heater). If hot air makes a difference, compression is a likely issue.

Adding your location to your profile has benefits: another member with test equipment may be local to ya.

[ad]

Well, I would love to do the pop test, but where I work, this stuff is so obsolete we dont have the equipment anymore

That's a weird statement to me as the VE pump was used on VW, Mercedes, Cummins, maybe others for about 20 years. If you have a pop tester at all, just use one of your fuel lines to connect it.
If you dont have a pop tester and compression tester at your shop, then you dont really have much of a diesel shop.
Well I guess this is a moot point now since you already have new injectors on the way.

As for compression, Im actually trying to avoid that scary venture, Ill consider it at last resort,

I dont understand this statement and completely disagree.

Compression is the basis of operation in a diesel, without it you have nothing.

I dont understand what is scary about it?

You are replacing the injectors!?!?!?! Then all the work is already done. Just do the test before you put the new ones back in. Buy a cheap $50 tester and know for sure rather than always wondering. If it does turn out to be low in one or more cylinders, it might totally change your plans. (i.e. : no sense in putting new injectors and rebuilt pump in an engine with only 200 psi)

....And as for the sudden loss of compression not likely, I thought the same thing about an old engine I had. It was running fine with decent compression but it was engine that had sat for a few years. The little bit of rust in one cylinder caused a ring to chip and the rusted area was so scored so deeply that there was suddenly very little compression after thousands of mile of running ok. One day it just became very hard to start and only had 3 cylinders firing.

Now having said all that, I will admit that fuel & air problems are more common than mechanical problems, but in this case since you will already have the injectors out, and showing no bubbles in the clear lines, there is no reason not to do a comp. test.

[82vdub]

I agree with compression. When you know the compression is good, then you can focus on other solutions. Until you rule it out, it could be a factor.

[killerrabbit]

Okay, now that I found where, I updated my profile,

as for the lack of equipment at my shop, I work for a VERY large truck rental and leasing company, the oldest trucks in our fleet are "05" models and all have modern electronic injectors. we do have reefer and APU units with injection pumps, but on the rare occasion one has an injector/pump issue we send them to Thermo King or Carrier. at the dealership I used to work for though, we had all that stuff, my current employer literally threw the stuff out about ten years ago. (I'm sure someone went dumpster diving), I know how to make a pop tester out of a jack, I just don't have the time right now.

As for compression, I suffer greatly from the effects of "Murphy's Law", so logically as long as I don't check it, the compression will be fine, but as soon as I check it I will find out I need a complete overhaul, and cant afford it.(Im not serious of course, but you get what I mean)
I am currently toying with the possibility of sleeving a cracked block I have and building a turbo block out of it. (Ill have to install piston coolers as well), but as I said, "cant afford it yet"

I am looking into finding a tester, but for the meantime Ill assume its okay and that my problem was in the pump. I removed it today, and there was A LOT of slop in the bushings. while trying to pop the pulley loose I was rocking the whole shaft back and forth about 1/16 inch, I'm hoping maybe the front seal was allowing air to bleed into the pump when not under pressure, causing a large air pocket to form in the pump when it sits, but when running it would be held tight by pressure and wouldn't leak fuel out.

the main reasons I don't suspect compression are, It was not smoking, or using oil (other than fuel smoke at startup that went away in a couple minuets), and it wont even start when the engine is warm, and I mean still 90 degrees or so, even when I plug in the block heater and its toasty warm under the hood, it just cranks, or cranked till the starter quit.

Today I also went through the valves, and all four exhaust valves were too tight, .005-.007, (spec .014-.018) so I swapped shims around with another head till they were all within the correct range. Although it says that is the spec on the fender sticker with engine HOT, my chilton says Cold, same numbers. All the Intakes were within tolerance.

My pumps built, and injectors are on the way,

[82vdub]

The play in the IP shaft could definately be a way for air to get into the system. Have you verified that there's not a restriction in the fuel line that coupled with a loose IP shaft, could be siphoning fuel back to the tank when the engine's off?

[Fatmobile]

Yeah, you can't just put clear line going into the pump.
You need clear line between the injectors and going out of the pump toward the tank.

A leaking small line between the injectors could be letting air in so fuel syphens back to the tank.
The cold is making it more brittle and leak more.

Turn the engine by hand to figure out compression.

[Quantum-man]

Unscrew your fuel lines and reattach them upside down.
Add four different injectors, to save you removing the ones in the head.
Crank after car has not been started for some hours and see if fuel is priming and fireing those injectors.
Actually to save unnecessary cranking, crank with lines attached but injectors loosely attached to prime the lines. When lines dribbling tighten nuts and crank some more.
An injector carries about the same volume of fuel as a line, so it won't be immediately spraying.
Once spraying; leave for however many hours you think appropriate, and then try recranking.
If the injectors don't respray within one revolution then pump is loosing it's prime.
Don't worry about internal pump pressure. The pump can operate with from low pressures.
My pump was down from 45ish [spec] to 18psi @ idle and still operated.

[TylerDurden]

...I am looking into finding a tester, but for the meantime Ill assume its okay and that my problem was in the pump. I removed it today, and there was A LOT of slop in the bushings. while trying to pop the pulley loose I was rocking the whole shaft back and forth about 1/16 inch, I'm hoping maybe the front seal was allowing air to bleed into the pump when not under pressure, causing a large air pocket to form in the pump when it sits, but when running it would be held tight by pressure and wouldn't leak fuel out.

Slop in the mainshaft will let in air when the IP is sitting and often more when running. The seal keeps air from entering the suction side of the lift portion in the IP.




The seal is not too hard to replace. If the 1/16" play was observed at the tip of the shaft, it might be worth the price of the seal to try.

[Fatmobile]

That TylerDurden is great with the pictures isn't he???

The yellow area in the top pic shows how the front of the pump input is connected to the output of the internal pressure regulator and the area behind the mainshaft seal.
That's why if the seal is bad you will often see air coming from the front of the pump after shutdown,..
as fuel syphens back to the tank..