Official Fuel injection questions thread

[Bennym777]

No vacuum leaks, but she cut out today at idle and didn't want to start when I got her home. Fired right up about an hour later. I am going to change the fuel filter (have no idea how long it's been there). IF continues will test the fuel pump out. I believe they are about 40psi?

[VW_Jimbo]

Try the fuel filter if you have been lacking in the maintenance department. If the car runs good through the higher rpms, I would not think the fuel filter or system are faulty at a lower demand. Unless one or more injectors are partially clogged or encased in carbon. I think you may need to have a carbon cleaning completed. Also, spark plugs look like? Air filter?

I am sitting here thinking about that hard start. Almost sounds like the IAC is not functioning correctly. Those IACs get blocked up with carbon deposits, so do the Throttle Bodies. You may want to spend some quality time cleaning the carbon out.

If for some reason the IAC is not finding it base setting correctly and is not closing the idle air flow off at the right point, it may allow too much air in during start up and at idle, killing the engine or making it stumble due to running too lean. Really leaning towards the IAC.

Coolant level good? No leaks? Check the base resistance of the CTS. Coolant temperature sensor. It may be skewed and causing a lean condition. Be sure coolant is available when you remove it. I have seen them plugged off from lack of maintenance.
_________________
Jimbo

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

[sawed off]

Can anyone on this thread tell me how to test the sweeping resistance on my afm. What pins to touch, plugged in or not, I have asked on the 68 and up forum but no one seems to know.

[busdaddy]

Resistances listed near the back of this: https://www.thesamba.com/vw/archives/manuals/afc_f...Manual.pdf
Or maybe this is more suitable: http://www.itinerant-air-cooled.com/viewtopic.php?f=50&t=7761

Just what are you doing that you think you need to OHM it?
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[sawed off]

I have 3 afm. I have afr meter in tail pipe. 1 out of the 3 afm works awesome, I can get 14 -15 to 1 air fuel ratio from idle on up, runs great. The other 2, I can set idle afr around 14 to 1 or 15 to 1, but as soon as I bring rpm up slowly they both go very rich, like 11-12 to 1. I want to test the sweep and see if theres something gone junk.

[ShakeyVW]

I had to remove the cooling tin to replace the alternator on my wife's '76 FI Super convertible. While I have it apart, I'm replacing the oil cooler seals, and trying to eliminate some minor oil leaks.

Can anyone tell me how to remove the intake air distributor? This is the item that the alternator sits on. Bentley's simply says to remove the four nuts. There are three on the outside, and one in the throat (you have to take the left side off to get to it). I can find no other attachment, and the throat stud completes the pattern with the other three.

It this thing just stubborn, or am I missing something?
_________________
-Kevin
1972 Yellow Super Beetle Convertible (daughter)
1976 Blue/White Super Beetle Convertible (wife)
...sometimes I get to drive one

[corkywillis]

I have a 1978 VW Superbeetle FI and am only getting 9.5 volts to the fuel pump. Double relay seems to be good and fuel pump is new and works when I put 12 volts to it off the car. Will the pump run on 9.5 voltage with the car being a 12 volt system ? I cant hear if it runs while cranking the engine. Can anyone help?

[busdaddy]

[paquinbrad]

First of all, thank you @busdaddy and others for taking the time to share knowledge. I have owned a 1979 bug for 3 years and figured when I had fuel injection trouble I'd convert to a carb - I have changed my mind and want to keep the car original thanks to the knowledge being shared.

I have arrived at my first FI issue.
Last fall the car would intermittently not start, most often when hot. Would start with starter fluid then keep running.

This spring it wouldn't start. Car fires on starter fluid but stops running as soon as starter fluid is gone, so I know I have spark.

I tested the double relay per Bentley manual, 88d does not light when the key is turned, nor does 88b...so I believe my double relay needs to be replaced. I can hear the relay clicking when the key is turned, so I have some doubt the issue is the relay.

While testing the relay I came across two weird things that I'd love your input on. When testing current supply between 85 and 88y, instead of my test light lighting up...it looked like a short with a glow at the tip of the test light and the light didn't light which I only let happen for a fraction of a second for fear of destroying the harness (when i put my test light across the pos/neg battery terminals the light comes on bright with no sparks).

Also, there is a red jumper wire from 88y to 88z...Is that how the relay was wired from the factory? I know both 88y and 88z should be powered by the battery, surprised to see a jumper.

Sorry for the long winded question, thank you for your time.

[busdaddy]

Welcome!
The loop between the plugs sounds like the one VW put there, unless it's hacked in with crimp terminals or something don't worry about it.
The glow at the end of the test light probe is very odd, sounds like a test light flaw or maybe you inadvertantly touched another wire you didn't see? A properly functioning test light can't do that, it just lights up.

Your starting issue could be a number of things, perhaps start with a fuel pressure gauge on the line to the CSV (any 0-50psi gauge will do, Home depot has them in the plumbing dept, you'll need a 5/16" hose barb as well) and see what the fuel pressure is doing when static and while cranking. From there we can move on to pump and relay testing once we have some pressure numbers.
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[paquinbrad]

Thanks for your quick reply.
I left out what I guess is a key point. At first when the car wouldn't start I checked the ground from the harness (terminal 85) to the battery and found it was bad, the wire was broken going into the spade connector to the battery.
I replaced the spade connector, and the car fired right up and I drove it about 30 miles, and pat myself on the back for being such a great mechanic.
A half hour later I went to move the car into the garage, and it wouldn't start. So I know the fuel pump and the rest of the system is capable of working as it should....but is not getting the signal to turn on when the ignition switch is on or at start position.

[busdaddy]

OK, 2 different things activate the fuel pump, lets see which one has quit.
In the DR plug there's a red/black wire that connects to terminal #86a, use your test light and confirm it gets powered while cranking (doesn't have to be plugged into the DR to test), if not confirm the other end is connected to the #50 spade on the starter.
Then with the key on and the DR plugged in depress the spring loaded flap in the AFM through the rectangular hole under the air filter element, a chopstick works well for this and won't damage anything. You should hear a click from the DR and hear the fuel pump running as long as the flap is depressed.

L-jet will usually start even if 86a is disconnected if it can draw enough vacuum to open the flap in the AFM, some owners go for years never knowing it was disconnected. But if vacuum leaks add up to a point where the flap won't open while cranking enough to start the pump the car gets hard to start. This usually is combined with a leaking check valve or weeping FPR that allows the fuel pressure to drop to zero while parked.
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[paquinbrad]

Confirmed red/black wire gets voltage while cranking, harness pulled out of DR. No power at 88D under same condition.
With DR plugged in the old 'chopstick to the AFM' trick immediately started the fuel pump with ignition on. I swear I tried this after reading the thread this weekend and I didn't initiate the pump, maybe I didn't open it far enough or the problem is truly intermittent.
My vacuum lines look old/loose on the connections - they need to be replaced as you mentioned.

So I should replace the DR as it's not powering 88D, and replace vacuum lines. For the FPR, I should get a gauge and monitor lead down rate? Not sure what the check valve is - is that part of the FPR that I'd find defective with a fuel pressure leak down test?

Thank you again - let me know if you have a favorite coffee shop I can call in a gift card for you.

[busdaddy]

No gift cards required, happy to pay it forward, thanks anyways.

Maybe your next step is a test light of some sort connected to the fuel pump leads at the fuel pump?, see what it does cranking and driving around. Before I replace anything I invest some time into going through every single wire terminal and ground cleaning them up shiny, greasing them and reinstalling securely. Look carefully for broken wires where they meet the terminals even though the insulation is intact, and terminals that push back out of plugs and don't make contact when plugged in.
You can also try jumping to the red/black wire with the DR plugged in and the key on and see if the pump runs (caution, if that wire's still connected to the starter the car may move if it's in gear).
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[bgbugman72]

So I am getting my car to start but then it dies right after. Did all the above tests everything tests ok. But like I said does right after strat up like something is shutting off power to the relay. I have an old relay that I can hold down the contacts and I can keep the car running no problem. Anyone have any ideas?
_________________
'72 Super Beetle.
'71 Bus
Wish I still had my '77 sunroof from high school.
78 vert for my wife

[busdaddy]

[bgbugman72]

I did The flap trick. Relay actuates like it should and cranking the motor pulls enough to move the flap and closed the contacts in the AFM
_________________
'72 Super Beetle.
'71 Bus
Wish I still had my '77 sunroof from high school.
78 vert for my wife

[VW_Jimbo]

[bgbugman72]

Filters new. I had this motor running just fine in my stand then I put it in the car and now this.
_________________
'72 Super Beetle.
'71 Bus
Wish I still had my '77 sunroof from high school.
78 vert for my wife

[busdaddy]

Sure sounds like the AFM, but try a jumper to the coil #15 to rule out the ignition switch, that's something that wasn't part of your test stand, right?
_________________
Rust NEVER sleeps and stock never goes out of style.

Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
Stop dead photo links! Post your photos to The Samba Gallery!

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