Update: Troubleshooting EFI issues on 1.7l D-jet

MarkRobinson · 05-17-2007, 06:03 AM

Ok, I found another culprit.

First, my head temp sensor was bad: was never allowing the mixture to lean.

Second, I sent my fuel injectors out for a rebuild/flow, one was completely bad: no electrical activity within with power, so, for $60, Autozone has one coming for me.

I could blow through it barely, which means it was dripping, barely spraying all the time, which is why the car was still running, but since heat expands items, it might also be the reason the car ran excessively rich once warm (15-20m into driving). We'll see, it's going all back together with new braided 7mm EFI hose, EFI hose clamps, & everything painted.

Mark

hardflex · 05-17-2007, 09:48 AM

so your Head temp sensor didn't vary the resistance as it warmed Up?

a leaky injector would likely make just 1 cyl rich, not all of them.

a leaky cold start valve could make all burn rich though, as will a faulty MPS (ask me how I know) . So check both of those as well.

MarkRobinson · 05-17-2007, 10:17 AM

MPS appears ok, decel valve appears within spec, AAR valve appears to be working ok, no resistance on a hot head temp switch, & a internally leaking injector: I had one cylinder running lean, that was probably it. I'd lose a cylinder or two & the car would then die at idle, once the car was warm. Fuel consumption was suggestive of a EFI'd V8 rather than a flat 4

hardflex · 05-17-2007, 10:30 AM

Looks like you have def. found your trouble then.

MarkRobinson · 05-18-2007, 04:52 AM

I hope so! I need to start working on my neglected 930 that's hogging my lift.

Mark

Tobra · Tobra's Garage

Look at the 7mm ID, 13 mm OD line they have here. Spendy, but better than the cloth braided stuff, IMHO. That clth covered stuff is so 1950's, which is okay for music, but, maybe not fuel hoses.

I believe there was a recall of the cloth braided stuff for 914's, but none of the North American VW products.

Bleyseng · Bleyseng's Garage

The fabric hose soaks up any water that hits it including the acid water. Rots it out quickly so Porsche came out with the rubber coated acid resistant fuel line to solve this problem.

People seem to think the fabric stuff it cooler or more OEM but its not correct unless you like the problems of the fabric hose.

MarkRobinson · 05-21-2007, 05:13 AM

Crap, ok, next problem: I've completely, completely gone through the whole top of the engine: all new fuel lines, rebuilt fuel injectors (one was bad, replaced with an Autozone "GP Sorensen" injector, all new hoses, etc.

My rebuilt distributor wouldn't fit due to the condensor being in the way, so I had to move to the opposite side of the disty to get it to seat. Wierd.

Anyway, engine fired up, but still running very rich (haven't verified fuel pressure, nor the "base setting" on the potentiometer on the ECU, but was running on 3 as one of my rebuilt injectors became seized within the last week. Ok, wierd.

Un-seized the injector, car runs ok, however, my new injector is flowing less than the others as I actually achieved some detonation while test driving. My new injector's ground strap was white, while the other plugs were about as black & sooty as I've ever seen them.

Anyone else use the GP injectors before? I just double-checked the PN, it is indeed correctly stated on a second part number source for the 1.7l: 800-1108N. I understand the 2.0 injectors are larger, wondering if I have 2.0 injectors in my car...the part numbers on these yellow top injectors are: 022 906 031 A and the Bosch # is 0280 150 009.

hardflex · 05-21-2007, 06:26 AM

the yellow injectors are 1.7's. 2.0 inj are green i think.

i would be inclined to put a bosch oem injector in there. 1.7 ones are plentiful and cheap, I have some extras if you need some. That way you'd know voltages and resistances would be to spec. The fact you're having as much trouble with ind. injectors makes me wonder if you have some grit in the system that's clogging them.

disconnect and plug the fuel line to the cold start valve, in case it's leaking.

MarkRobinson · 05-21-2007, 07:31 AM

I tried the cold-start disconnect: didn't do much, but #3 (new injector) was very lean compared to the remaining 3 which were freshly cleaned though black & sooty (the spark plugs).

Last week I received back the original 4 injectors, which had been balanced & flow-matched, though #4 was dead, hence the new injector from Autozone. I'm semi-inclined to go buy 3 more GF injectors.

Mark

Bleyseng · Bleyseng's Garage

Busdepot.com has the Bosch 1.7 injectors on sale for $39 which is a steal.
you have to look hard to find them on their site but use the 022 part number to search.

Forget using Autozone injectors as many people have had problems with those injectors

MarkRobinson · 05-21-2007, 07:59 AM

Excellent advice, thanks!

hardflex · 05-21-2007, 10:54 AM

to me, everything points toward a bad MPS if everything else is as you say. find someone with a spare and try it on you car.

MarkRobinson · 05-21-2007, 11:14 AM

well, doesn't explain the one lean cylinder with the new injector. I'll buy one from the before mentioned bug place to replace my dead one, as the other 3 are freshly flowed.

MPS holds vacuum pretty well, not sure what other tests to throw it's way.

mark.

MarkRobinson · 05-21-2007, 11:18 AM

Ouch, $196 per injector as busdepot.com currently....hmm, might be better off buying 3 more new injectors from Autozone

hardflex · 05-21-2007, 11:47 AM

wow I have a gold mine in parts in the back, then.

one lean cylinder means the injector is not working right, because the ECU sends the signal to a Pair of injectors at the same time, and if the "lean" one were working I suspect they would all be too rich. You've checked the CHT, and cold start valve, it's a rebuilt distributor (trigger points), so that leads to the MPS, in my opinion. check the part no's, and check to see if the plug has been drilled out, maybe someone, like myself, has adjust it to meet their purposes.

MarkRobinson · 05-21-2007, 12:00 PM

I emailed BusDepot just to clarify, but have not heard back yet.

If the banks of injectors are bank-fired, then I can swap the leads to the injectors to verify that I don't have a weak signal in my one lean cylinder bank. I can also swap the plugs to eliminate the possibility of having a poorly-conducting plug (I've had bad plugs before).

What's the CHT? Sorry, still learning my 914 acronyms.

My rebuilt distributor cam with used Trigger points, vacuum canister, points, & condensor: not bad for $69 right?

Drilled out which plug, the one on the MPS? I remember the epoxy being intact.

Mark

hardflex · 05-21-2007, 12:41 PM

they fire like 1 and 3, 2 n 4, together, not each side but across the motor. and yes, you can switch the plugs to test the electrical signal.

you have me wondering though, you said you'd lose 1, then 2 cyls and it would die. Have you checked the grounds on the top of the engine block? particularly the one connected to the injector that is lean firing.

The epoxe plug yes. If it's intact, I would just cross check that it's the right part number, mostly.

CHT = CYLINDER HEAD TEMP sensor... you replaced it.

MarkRobinson · 05-21-2007, 12:47 PM

yes, new cylinder head temp, new oil pressure switch, cleaned the ground wires (3??) that connecto to the splade connectors at the top bolt under the intake manifold. CHT was dead with heat, car now idles, though idles at about 1800rpm.

TB is shot, lots of play in the shaft, so ordered a good used TB from 914-parts.com

Bleyseng · Bleyseng's Garage

http://busdepot.com/details.jsp?partnumber=311906031B