Official Fuel injection questions thread

[Maltboy!]

[plextor]

I'm debugging some sluggish start issues on my '75 super and found that temperature sensor II seems to be faulty.

Instead of the ~2.5KΩ at 20ºC it's reading 1.2KΩ, which is the normal reading for 40ºC. That would explain a lot of the behavior I've observed over the summer/fall.

No big deal, these are still available and cheap... what surprised me when I was taking the old sensor off is that it doesn't seem to match the orientation in the orange Bentley manual. Instead of coming off the head vertically above cylinder #4, it is coming off to the side. Is this normal for a '75 EFI Super or have the heads been replaced from something else at some point in the past?

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1975 VW La Grande Bug (Super Beetle, 1600 EFI, owned since May 2021)

[busdaddy]

What's the part number cast in down behind the rockers?, maybe late type 3?, it's not the common place for type 1 L-jet.
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[plextor]

[busdaddy]

Ahhhh...
It's a VW Brazil replacement head, not meant for L-jet but someone drilled and tapped that boss on the side of the rocker box, better than some of the alternatives. Does the RH head match?, I think the valves are different size than stock for that engine.

For reference the 68/69 D-jet head has the sensor below the exhaust port:

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[plextor]

yep same on both sides. should be interesting when/if a rebuild happens in the future.

needless to say, with a new temperature sensor the engine starts up a whole lot better. Not modern-car better, but closer!
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1975 VW La Grande Bug (Super Beetle, 1600 EFI, owned since May 2021)

[christyxy]

Hey everyone, when I bought my '79 super bug I wasn't all that familiar with the fuel injection system and how it was supposed to look, I've noticed that a few parts seem to be missing from mine compared to pictures I've seen of others, can anyone advise what I'm missing and how important it is?

It seems to run ok, if a bit rich (I just replaced temp sensor 2 and backed out the idle and CO screw a bit which have helped a lot)

Pics below annotated with the spaces missing parts or that look patched up!

There's a gap in the tinware by the left arrow for something to be bolted in, but I don't know what... and there's a bit of metal that's been bolted on to cover or in place of something else (2 bolts above the right arrow).

Can anyone advise? Is there anything else that looks out of place on my engine?

Cheers!

Christy

[busdaddy]

Your EGR system has been removed, the 79 would have used the mechanical valve, not easy to find a good one lately, but if you want it for show even a leaker will do if you put a solid gasket between it and the manifold.

Rich running could be related to fuel pressure, or a bad pressure regulator, put a 0-50 PSI water pressure gauge into the cold start valve hose and see what it's doing. Also test for a change when you pull the vacuum hose to the FPR off.
Hopefully you find an issue there, because the next suspect is a messed up AFM from some "expert" trying to compensate for a vacuum leak, that gets more complicated to repair.
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[VW_Jimbo]

Sounds like some extra air is getting into the intake manifold. Or you have a vacum leak. Start searching. Some of them make a whistle noise, under the right conditions. Others respond to shots of starting fluid and some remain “at large” until you smoke them out!

Use a smoke test method similar to this one.
https://www.thesamba.com/vw/forum/viewtopic.php?t=620083&highlight=smoke+test

Or If you some cigars, that may benefit you. You could puff on the cigar and blow the smoke into the intake system, keeping your eyes peeled for latent smoke exiting!

Good luck!
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Jimbo

There is never enough time to do it right the first time, but all the time necessary the second time!

[zoti]

I am trying to source a good quality new S boot for my 79 convertible. Part #043129617A

The one I received from CIP is great but the hole for the crankcase vent hose and sleeve is too big and I get a vacuum leak. The original one (made by VW) has a hole that holds the metal sleeve tight.

I am also looking for the hose that goes from the sleeve to the base of the oil filler. I believe it is part #181-129-651C but need to confirm.

The picture shows my original S boot with the metal sleeve. You can see the step down in the hole in the second picture. The new boot does not have the step down.

[busdaddy]

Sadly it's par for the course with CIP, I'm not aware of anyone who sells a better version, the competition likely all sell the same part from the same manufacturer. Airhead has been pretty good about getting things right, perhaps ask them about their version: https://airheadparts.com/vw-part/intake-sleeve-elbow-043-129-617-a/ They may have the hose too, I didn't look.

If it's the same part you may have to build up the sleeve/nipple with heat shrink or RTV to make it fit better.

I guess we should all still be thankful that any parts are available for a 43 year old car, even if they are kind of shitty and need tweaking to make work, things could be worse.
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[Gr0unded]

[admvw78]

I'm in the midst of working through the wiring after a fuel pump stopped working on my 78 Super convertible. Double relay checked out after working through the process. Have yet to hardwire the fuel pump to see if that fixes the issue, but one oddity: All the spades are spoken for on the plugs that go into the double relay, but I have two left over white wires going through the firewall to the engine. They are factory terminated with spade clips and insulating covers. Anyone know what those are supposed to connect to? Are they missing a home, or are they diagnostic wires? I didn't unplug them between the time the car ran and when it stopped, so I don't think that's the root of the trouble, but do wonder what their purpose was. I can do some tracing and hunting if I need to, but thought I'd start by asking.

[Gr0unded]

[busdaddy]

[zoti]

Sleeve to S boot issue solved by putting some 25mm shrink tube on it and trimming it to length.

The sleeve is originally 22mm in diameter. The shrink wrap makes it 24mm which fits perfect.

Car is running again.

How it fit before

[admvw78]

[quote="busdaddy"]

[busdaddy]

Much of what you describe sounds like a vacuum leak, possibly combined with a faulty temp sensor #2 (TS2). Although a tune up and valve adjustment is always worth the time to try first. Think twice about Pertronix, some don't produce a wave pattern that L-jet can read properly, all sorts of minor running issues can result. Points always work, and speak the language the system understands.

Smoke test for vacuum leaks: https://www.thesamba.com/vw/forum/viewtopic.php?t=620083&highlight=smoke+tester
TS2 test: https://www.thesamba.com/vw/forum/viewtopic.php?t=694879&highlight=sensor+ohms

FI tips?, there's lots but a few major ones are test and confirm a part is actually broken before changing it, new parts usually suck and OG parts rarely break. Don't just shoot the parts cannon at it, it makes diagnosis much harder, with a few basic tests you can narrow it down to the cause.
If you don't know the age of the rubber fuel lines, or they are more than a few years old change them all, use hose rated SAE J30r9 or higher and ABA style fuel injection hose clamps.
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[admvw78]

Thanks for the reply. Regarding Pertronix, I agree that well adjusted points should work fine. They can usually be tweaked to keep it running, and if something does go, keeping a spare condenser, points, and rotor in the glove box is cheap insurance.

Other notes:

1. I think it's earned some new hoses (some are original fabric covered rubber). I've tried a butane vacuum leak test, but couldn't find anything that way. The smoker is an interesting idea, though. What's the best source SAE J30r9 hoses?. Most of them are friction fit. I'll plan to add the clamps when I do them.

2. There's a small sliver relay box with a handful of wires coming and going under the rear seat opposite side of the battery (looks like half the size of the double relay and attached to floor pan with a screw through a tab). Can anyone give me the quick 101 on that box? I can snap a photo if needed.

3. In the course of troubleshooting, I discovered that the fuel pump hoses have sprung leaks and need replacing (they were replaced with new 15 years ago when I restored the vehicle). My previous hose routing left something to be desired. Any tips or best practices (or best hose vendor) that you'd recommend seeing as I have to do it over?

Thanks again,
Adam

[busdaddy]

The hoses all had clamps when it left the factory, the short ones between the fuel rails and injectors had pushlok ferrules on the injector ends, you can carefully split those with a dremel and use ABA clamps in their place.
Belmetric and Flennor are good sources for metric hose, if you are in a panic your local FLAPS will have 5/16" which is so damn close it really doesn't matter. The stuff isn't cheap, but it's impervious to ethanol and should last many years (inspect regularly anyways just because).
Or just buy the whole kit from Germansupply.com, they usually include hoses, clamps and a diagram on routing and lengths.

The relay on the LH side is for the rear window defogger.
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