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Fuel Injection Gremlin '79 Super
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abl1111
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PostPosted: Thu Jan 23, 2020 9:26 am    Post subject: Fuel Injection Gremlin '79 Super Reply with quote

Quick Synopsis ( I had this in a cold start topic, but this has morphed into a FI problem )

Car started to run like crap after having starting and running perfectly for years. Only change, I used my bother's double relay to test it's function. Could be odd coincidence or it triggered something.

Checked all hoses and made sure all FI connections were on right. All looked good. Still ran terrible.
Note - absolutely nothing had been touched other than swapping the relay - also that the weather hit a real cold spell.

AFM - When at idle, I pulled the main elect plug off the AFM, idle raised and it literally purred. As soon as I put the plug back on - ran terribly again - even stalled. Took her for a spin locally, ran well, but did not hit top end speed. Did this with a spare AFM - same result.

Checked battery ground and the small brown, FI wire that connects from harness to Ground battery. Double relay inspection is a bit more involved to do properly - I did inspect and all 'looks as it always has.

Checked the alternator grounds too.

Tested the cold start valve - there was juice today ( where previous test, there was no juice ) The car started right up. Test I did --> Disconnected the CSV plug, grounded one and test light in other. Ran starter - light lit. After the high RPM, she came down and started to run rough ! Almost stalling. I have not checked the valves yet, I did check points and the timing with a strobe light ( 5 deg ATDC ).

A thing I did notice -- > after rough idle, the car stalled, so the key was on, and I heard the fuel pump still running and a 'gurgling sound' around the fuel pressure regulator near the fire wall, I could hear the sound of the flow of fuel mixed with air - sounded like a leak would, but there is no fuel.

During this, and knowing the AFM controls the fuel pump, I put a screw driver into the AFM to move the flap, and when I did, the fuel pump stopped and so did the sound.

Shouldn't the fuel pump turn off when the car stalls ?

Lastly, the exhaust smells rich. And, upon acceleration it's sluggish. This am, she backfired a bit when I pushed on throttle.

Where should I focus ? I am at a loss.

My thoughts - I want to check CSV for leaking. Check term 50 connection at starter solenoid and at relay.

Thank you
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PostPosted: Thu Jan 23, 2020 9:36 am    Post subject: Re: Fuel Injection Gremlin '79 Super Reply with quote

When was the last time up?

Compression numbers after valve adjustment?

Fuel pressure?

Spark test?

My suspicion is that you have weak spark, but without knowing the condition of the other systems it is hard to say. I would test everything to determine what system I would be chasing and then make an educated guess.
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PostPosted: Thu Jan 23, 2020 10:28 am    Post subject: Re: Fuel Injection Gremlin '79 Super Reply with quote

Donít know why youíre jumping straight to FI. You have said nothing about going through ignition system first.
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PostPosted: Thu Jan 23, 2020 10:44 am    Post subject: Re: Fuel Injection Gremlin '79 Super Reply with quote

abl1111 wrote:

AFM - When at idle, I pulled the main elect plug off the AFM, idle raised and it literally purred. As soon as I put the plug back on - ran terribly again - even stalled. Took her for a spin locally, ran well, but did not hit top end speed. Did this with a spare AFM - same result.
......................

A thing I did notice -- > after rough idle, the car stalled, so the key was on, and I heard the fuel pump still running and a 'gurgling sound' around the fuel pressure regulator near the fire wall, I could hear the sound of the flow of fuel mixed with air - sounded like a leak would, but there is no fuel.

During this, and knowing the AFM controls the fuel pump, I put a screw driver into the AFM to move the flap, and when I did, the fuel pump stopped and so did the sound.



There's some useful clues here, the pump should stop when the engine does, if the flap in the AFM is binding and not fully returning to it's stop the pump will run on and the mixture will also be effected. Unplugging it likely leaned it out which improved the idle. Any carbon or oil build up on the flap or in the duct it operates in?

On a side note that gurgling sound may be telling you it's fuel filter time, or that there's a floaty in the tank partially blocking the inlet.
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abl1111
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PostPosted: Thu Jan 23, 2020 2:48 pm    Post subject: Re: Fuel Injection Gremlin '79 Super Reply with quote

Let me start by saying this as a baseline. The car ran PERFECT ( just the day before ). The (2) things that changed were: I installed my brother's double relay to test it for him. The ambient temp dropped to the 20's. She has always started in cold weather just fine.

I just started car a few moments ago. It did not go through its normal, high idle start and kick back down - auxiliary air valve sequence. Which was odd. She started pretty quickly - idled OK, not great - then, at or around operating temperature, progressively got worse - then stalled.

Will check valves and fuel pressure this weekend.

Compression - I doubt it's a mechanical/ cylinder/ compression issue at this point.

Interesting - I pulled the #2 injector boot and did not hear much of a difference in idle ( always afraid to do this near the spark plug wires ! ), This is concerning ! Thoughts on this ?

I also clamped cold start valve fuel line to rule our leaky cold start valve.

As for FI vs ignition system. I've always sort of erroneously blended them together in thought. You mean dizzy, cap, rotor, points, condenser, coil, spark plugs ? I checked points, inspected cap, rotor - dizzy has always been fine. Coil ?

Ooooffff - this is odd.
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PostPosted: Thu Jan 23, 2020 4:18 pm    Post subject: Re: Fuel Injection Gremlin '79 Super Reply with quote

abl1111 wrote:
Let me start by saying this as a baseline. The car ran PERFECT ( just the day before ).


Yeah but so what? Very Happy
They always run perfect right up until they don't. That's like the guy calling tech support saying "it worked fine yesterday!" Very Happy

So you pulled #2 injector boot and didn't notice much difference. Try the same trick with the spark plug wire instead and see what you get. If no difference in rpm, pull the plug out and make sure it's not fouled or closed up.

Since this started happening after swapping around double relays, do consider the possibility that you have a poor connection in the double relay plug that you have disturbed in the swapping process. Give that a good check, make sure all the connectors are tight within the white harness plugs at the double relay.

Verify also that you haven't accidentally knocked a vacuum hose loose somewhere, that will definitely make it run like shit.
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PostPosted: Thu Jan 23, 2020 4:38 pm    Post subject: Re: Fuel Injection Gremlin '79 Super Reply with quote

Agreed, regarding yesterday vs today. I just have not had experiences where an issue arises just like that ( I've owned this old lady for over 36 years ).

I will double check everything ! It's in my cramped, one car garage, its been freezing out. Over the weekend, I'll pull her out and get into it.

Stay tuned.
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PostPosted: Thu Jan 23, 2020 4:39 pm    Post subject: Re: Fuel Injection Gremlin '79 Super Reply with quote

Check your fuel pressure. It sounds like your pump is not giving enough pressure.
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PostPosted: Thu Jan 23, 2020 6:21 pm    Post subject: Re: Fuel Injection Gremlin '79 Super Reply with quote

Will ck

What feeds fuel pump voltage ? I want to ck that too...
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PostPosted: Thu Jan 23, 2020 6:39 pm    Post subject: Re: Fuel Injection Gremlin '79 Super Reply with quote

Iíd disassemble the relay plug. One of the worst electrical problems I finally solved was when a turn signal relay was changed, and the curvature of the clamping section of one of the femal spade terminals cracked.
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PostPosted: Fri Jan 24, 2020 5:57 pm    Post subject: Re: Fuel Injection Gremlin '79 Super Reply with quote

abl1111 wrote:
Will ck

What feeds fuel pump voltage ? I want to ck that too...


The double relay behind the engine control computer gives it power. It sends power when the switch is in RUN position and the engine is running or cranking.

An easy way to check is to push the MAF flap with a screw driver. When the flap is open (air going through) it tells the relay that the engine is running because air is going through the MAF.

If the engine stops running for whatever reason, air will not go through the MAF and the flap will close disconnecting power to the pump via the double relay. It's a safety feature.

So I would connect a fuel pressure dial to the fuel line and check like that. I believe the pressure should be 30PSI but check in the manual as I might be wrong.
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PostPosted: Sat Jan 25, 2020 1:21 pm    Post subject: Re: Fuel Injection Gremlin '79 Super Reply with quote

Did not test fuel pressure yet, or ck valves ( can't pull car out - raining )

I have run quite a few FI voltage tests today. Some from the Robert Bosch L Jetronic Workshop Manual someone linked above, and some testing from Rob and Dave's Website ( Fuel Injection/ Double Relay ) - taken from Bentley.

I used a voltage meter as opposed to a light test to get actual volts. All tested good. One voltage test, the reading is of concern, another the Voltage seemed low.

Concern - L Jetronic Test, page 147 testing "Function of Main Relay Section" - 88a and 88z tested fine. However, 88c read .004-.005v. I would have thought this would be 12'ish. Cross referencing this, it looks like 88c is related to the Aux Air Regulator ( which as of this fiasco, has not been working properly. Of note - I tested this on (2) working relays and the results were the same ?! Also, while car was running, I pulled the plug from the Aux Air Regulator and it lit up a test lamp.

The Low test - from Rob and Dave's - ground to relay plug 85, test terminal 86c; at postion two of ignition, 12.1V, while starting 10.5v ( the 10.5 seemed low, but it could be the starter drawing voltage ?

One thing that was confusing to follow - Bentley - L Jetronic Test. --> page 146, diagram right bottom - ..' also ck voltage at terminals 43/1 and 43/2 against ground...' Where the h*ll are those ? Can't find them on any diagram.

Thx - I look forward to your advice...

- The Gremlin Hunter
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PostPosted: Sat Jan 25, 2020 5:07 pm    Post subject: Re: Fuel Injection Gremlin '79 Super Reply with quote

Yes, the voltage drop is likely starter draw, cleaning up the battery posts, body connections, starter terminals and both the ground strap connections at the nose of the trans can improve that, the fuse block wire terminals can also add some drop, clean them too. Big volt drops on cars this age are the result of multiple little drops, death by a thousand cuts so to speak.
88c is indeed the AAR, it's powered when the fuel pump gets power, was that test done while the engine was running?
This may help you in your Gremlin quest: https://www.thesamba.com/vw/forum/viewtopic.php?t=334340&highlight=relay+color

Have you checked that AFM yet to see if it's gummed up?
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PostPosted: Sun Jan 26, 2020 10:38 am    Post subject: Re: Fuel Injection Gremlin '79 Super Reply with quote

Here you go!

http://www.realtechsupport.org/UB/I2C/VW_L-Jetronic_Fuel_Injection_Workshop_Manual.pdf
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PostPosted: Sun Jan 26, 2020 2:40 pm    Post subject: Re: Fuel Injection Gremlin '79 Super Reply with quote

WOW - that was a good FI link. I'll have to really take my time to read it to understand it. My grasp of the electrical system and that of a voltmeter is at a " 101 level ".

Today I checked valves. There were (3) valves real tight in (3) cylinders. I adjusted all.

Checked points. Good.

Timed her - although, idle sounds much better at TDC and not 5 degrees ATDC. I set her at 5 ATDC.

Idle is low - I tried to adjust idle via the throttle body idle adjustment screw - but it had NO effect on raising the idle. I checked hoses for air leaks - can't find any. The idle is at around 825-850 - I want 950. That I can't set the idle from the throttle body is really odd. She is purring, but at a really low idle.

AFM - when running, I unplugged the AFM, the idle raises nicely ! As soon as I plug her back in, the idle goes down to 825-850 RPM. With AFM plug in, if I push the stator flap a little with a screwdriver, the idle raises to the sweet spot. This was tested on (2) different AFM's. With plug unplugged, I tried to adjust the idle screw - again, no effect.

Also, I did notice a fuel leak at one of the injectors, where the hose meets the injector ( I had them all re-hosed and inspected 750 miles ago. Only when I deflect the hose does it leak. I will repair ASAP.

I have not had the chance to check the fuel pressure yet. I have the hose and gauge - just not the time today.

Lastly, it does not seem that the thermo time switch or the cold start valve are working. I ran a bunch of tests and could not get a lamp to light for either. I grounded the thermo time switch plug and tried to get juice at the cold start valve plug - nada.

Jimbo - I've been reading that workshop and Bentley. Some of the L Jetronic directions for testing are vague. i.e. Testing the thermo time switch, I don't have a specific white wire - I have two. When testing resistance, on the (2) different wires, the readings are quite different.
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PostPosted: Sun Jan 26, 2020 4:51 pm    Post subject: Re: Fuel Injection Gremlin '79 Super Reply with quote

If the idle improves when you poke the flap a little it's too lean, either due to low fuel pressure or a vacuum leak, now you have to discover which one is the culprit. If the pressure checks out it's smoke test time.

Check that the retard side of your distributor holds a vacuum and moves the breaker plate when you suck on it, that may also be some of the issue. While you are at it check the advance side too.

The TTS and CSV only come into play when cranking, and then only if the TTS is very cold, warm ambient temps or an engine that has been run in the last few hours will shut the system off completely. Those white wires all have little tiny numbers printed on them an inch or so up from the plugs, if not the plugs on the TTS and CSV usually have tiny numbers down in the sockets beside the terminals too.
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PostPosted: Sun Jan 26, 2020 5:45 pm    Post subject: Re: Fuel Injection Gremlin '79 Super Reply with quote

OK, Getting somewhere. Off on a biz trip for the week. Will pick up as soon as I get back. Definitely will test the fuel pressure 1st thing.

If it is low fuel pressure - what might cause that ?

As for the TTS and CSV - they have always worked flawlessly up until last week.

TTS / CSV Theory -- - This is the way I see it - let me know if I'm correct.

TTS - the two white wires in the harness/plug - are they just in a loop for completing a ground ? Cold, the TTS allows for the ground to be continuous. Warming up would open that ground loop ? Then it would send that ground signal where ? before it gets sent to one side of the CSV ?

Then, where exactly does the 12V signal come from for the CSV ? I would assume that this 12V is always present, its just the TTS that stops sending the ground that would end the TTS providing fuel ---- Does this sound correct ?

I hope that makes sense ( and even better - correct )
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PostPosted: Sun Jan 26, 2020 6:03 pm    Post subject: Re: Fuel Injection Gremlin '79 Super Reply with quote

The idle screw on my 78 had no effect on the idle either. I replaced all the vacuum lines and now for the first time the screw will adjust the idle. I ordered a bunch of different sizes of silicone vacuum hose so some are red, some blue, some black but they are easy to work with.
Not suggesting that is your only problem, lord knows I had multiple ones on mine, but adjusting the idle on mine is now possible.
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PostPosted: Sun Jan 26, 2020 7:09 pm    Post subject: Re: Fuel Injection Gremlin '79 Super Reply with quote

Yes! L Jet is highly affected by ANY vacuum leak. No matter how small. As Busdaddy stated. Might be time for a smoke test.
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PostPosted: Sun Jan 26, 2020 7:39 pm    Post subject: Re: Fuel Injection Gremlin '79 Super Reply with quote

abl1111 wrote:
TTS / CSV Theory -- - This is the way I see it - let me know if I'm correct.

TTS - the two white wires in the harness/plug - are they just in a loop for completing a ground ? Cold, the TTS allows for the ground to be continuous. Warming up would open that ground loop ? Then it would send that ground signal where ? before it gets sent to one side of the CSV ?

Then, where exactly does the 12V signal come from for the CSV ? I would assume that this 12V is always present, its just the TTS that stops sending the ground that would end the TTS providing fuel ---- Does this sound correct ?


From the double relay thread I linked above:

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The TTS/CSV system is supplied with power when cranking via terminal 86, if the bimetal thermostat in the TTS warms from current passing through it during cranking (or engine heat) it breaks the circuit to the CSV.
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