more supercharger talk

[truckinwagen]

pressure gauge for the pump inlet is forthcoming, but I noticed that I cant hear the intank fuel pump anymore.

seems that it might have crapped out(will confirm with the pressure gauge)
a little search shows that I really dont want to spend the kind of money a new one costs.

anyone have a diesel tank pickup from a MK2 golf/jetta they would sell me?

[theman53]

That would make sense as it would be pulling it through the non working pump. Check your fuses and wiring on what you have.

[truckinwagen]

well, the lift pump is confirmed to be working, I installed a pressure/vacuum gauge in the feed for the injection pump(cost me $47, but is a good tool to have) and it read a good consistent 4PSI at idle, and 3PSI at WOT.

it read 3PSI even when it was stumbling and smoking and missing like crazy at 3000RPM.

so it is not a fuel line restriction.

if it was a timing related issue(crank pulley shift) it would be most pronounced at startup would it not?
it starts just as fast and easy as it did two weeks ago when it was revving fine...

so what is left?
something wrong internal to the injection pump?

-Owen

[rabbid79]

What if the return line back to the tank were partially plugged?  Wouldn't you still a get good pressure reading on the inlet side, but poor overall flow?

[truckinwagen]

maybe, but I am starting to think that the timing advance mechanism is screwed up.
either the advance piston is stuck, or the pump is not making enough internal pressure to advance the piston at higher RPM's

so my plan is to make the adapter for a pressure gauge to check the internal pressure, and if that checks out I'll take the advance piston cover off and see if it is stuck.

I'll check for a blockage in the return while I am at it too.

-Owen

[rabbid79]

Actually, I'm not sure my idea makes too much sense.  A blockage in the return line shouldn't limit the flow through the pump and out the injectors.  Might as well check it though.  It's easy enough to just blow on the line and listen for bubbles in your tank.

[truckinwagen]

if it was blocked it could cause too much internal pressure in the pump, which would over advance it, which could theoretically make it run like hell(much like to retarded would)

-Owen

[gldgti]

maybe, but I am starting to think that the timing advance mechanism is screwed up.
either the advance piston is stuck, or the pump is not making enough internal pressure to advance the piston at higher RPM's

so my plan is to make the adapter for a pressure gauge to check the internal pressure, and if that checks out I'll take the advance piston cover off and see if it is stuck.

.
-Owen

good plan!

i also just had a thought - if your boost guage has a vaccum setting you can plumb it to inbetween the charger and the inlet to make sure you have lots of air.

[arb]

I'd also double check the pump and cam timing.  Are they hyd lifters?  How's your oil pressure?

Good thought - when hydro lifters "pump up" or deflate from too much pressure will cause missing. I'm betting on issues in the IP though. Did you say you were waiting on a Giles pump Owen ?

[truckinwagen]

mech lifters, so that is not an issue, I'll check timing, but again would timing issues not be most pronounced at startup(cold)?

I would love to send a pump to Giles, but dont have the scratch right now(maybe when I come back from work this summer)

my boost gauge does not read vac, but I am confident it has enough air, the charger is always pumping more air than the motor needs regardless of if the bypass is open, so air is always rushing out the bypass never in.

-Owen

[truckinwagen]

it starts better retarded from the VW timing spec, which due to the camplate in this pump is sortof irrelevant.

and as for the timing not advancing as much, that may be true, but shouldnt be an issue because it ran so good and would rev just fine for weeks regardless.

I suppose the crank pulley could be failing, screwing with the timing, but it seems so rock solid.
I cant move it(relative to the crank) and there is no wobble in it at all.
I guess the only real way to know would be to pull the bolt and look at the keyway itself.

-Owen

[rabbitman]

if it was blocked it could cause too much internal pressure in the pump, which would over advance it, which could theoretically make it run like hell(much like to retarded would)

-Owen

I forgot to use my brains a couple years ago when I was messing with the advance/internal pressure thing, I removed the advance spring, put the cover back on and fired it up .

It took about two seconds for it to advance completely and yes it sounded very marbley. I had the brains to not floor it so I just revved it slowly and it didn't act funny at all, just rattled a lot.

In your situation even if it was advancing too much, or all the way, then as you revved it up it would eventually be advanced the right amount per the rpm..........

[truckinwagen]

good point.

I will focus on lack of advance, or crank pulley failure then.

-Owen

[truckinwagen]

unfortunately I did not have the gauge to use for the last timing setting(I had to return it to the shop I borrowed it from)

I just adjusted it until it sounded and drove best and called that good.

it does not sound or drive any different below 3000RPM, I would think that I would notice a change in starting, smoke, something?

I will go and look in the light to see if something looks off(might double check the pump mounting bolts while I am there too)

-Owen

[truckinwagen]

well, I think I found the problem.

the two bolts that hold the injection pump bracket to the front of the block have rattled loose, so the IP is hanging on just the flat part bolted to the side of the block.

it works fine during startup and low RPM running, but as the RPM's rise so does the tension in the timing belt. this tension flexes the bracket outward, shortening the distance between the pulleys and retards timing(faster than the pump advances)

I will pull the IP and re-install the offending bolts with blue loctite instead of anti-seize this time.
hopefully that will fix the problem.

-Owen