Official Fuel injection questions thread

[dgwduck]

Hello hopefully someone can help me on a 79 Beetle fuel injection car. I purchased this 3 years ago and replaced injectors, pump, fuel lines, tune up items pertronix and Bosch coil. I have put 10,000 trouble fee miles on this car in 3 years. 2 weeks ago when I pulled it outside to start And drive the car will not start. It will briefly run while the cold start valve pumps gas. I have used the manual and relays are good voltage at ignition and also checked voltage at plug in back with key on and cranking. I ohmed out the injectors and pulled out 3 and 4 and they spray fell when cranking. I also have a fuel pressure regulator and fuel pressure is present when I open air sensor door. I replaced pertronix unit cap rotor plugs wires and tried a different coil. This is odd in that I have fuel and can even smell it on plugs and remove wires from cap you can see spark. I also tested temperature sensor and was within ohm range. Got bored today so I pulled valve covers and adjusted valves. I have even replaced the air flow unit and ecu with another I have and nothing. Possible other things I have done but there is voltage and fuel and car does run for a few seconds.


PLEASE ANY HELP OR GUIDANCE WOULD BE APPRECIATED.

[busdaddy]

A big vacuum leak (like a crack in the S boot you can't see) can cause that, the fuel pump runs when cranking (separate circuit), but the leak robs enough vacuum that the flap in the AFM won't stay open enough while running.
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[dgwduck]

Thanks I will double check that tomorrow. I have had the s boot off a couple of times making sure the fit in the back was secure and throttle sensor was plugged in and not going to ground. Thanks and if any thing else is worth checking let me know.

[busdaddy]

If you can't find anything obvious a smoke test would help: https://www.thesamba.com/vw/forum/viewtopic.php?t=620083&highlight=smoke+tester
Aside from that a test light on the fuel pump wires (or a helper holding and feeling for action) to see if it remains running as the engine is dying (let go of the key) is a good place to start. Also try the test light between coil terminal #15 (black wire) and ground, does it remain lit when you let go of the key after cranking?, you could have ignition switch issues.
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[MuzzcoVW]

[busdaddy]

[dgwduck]

Hello and thanks for the help. The ignition test at the coil is something I had not tried. I ended up grounding the temp sensor and the car started right up. This is after I tried 2 temp sensors I had and the ohm levels were correct. Oh well. Now I am dealing with another issue I hope to get some advice on. I adjusted the valves to .006 and the car drove great for about 20 miles then the valves started clanking even when under moderate load. I also notice the temp gauge for the oil rose from 220 to 240 and the car idle went up around 10 k. I adjusted the valves first to .005 then to .004 thinking they were too loose. The timing was also checked and I tinkered with it as usually I run it a little high. Even after this the first 20 miles great with good power no valve noise and gradually the valves really rattle the car seems to lose significant power and the temperature rises 20-30 degrees. The idle rpms also rise and stay 10 k higher. Can anyone offer advice in what this issue could be? The car starts fine while cold and drives great until it seems like it warms up. Thanks

[dgwduck]

I forgot to add that I did install a nos Bosch temp sensor before driving the car on the 3 test runs. It was only grounded temporarily while trying to start

[busdaddy]

Hmmmm....., as Mr. Spock would say "Fascinating"....

You say it makes valve noise only under load?, sure it's not detonation you might be hearing?, overly advanced timing could cause it to get hot. The high idle when hot could be a vacuum leak opening up with temperature expansion, or possibly the mechanical advance in the distributor sticking, or both.

The strange part is it's too rich to start when cold unless you ground the TS2 wire, how's your fuel pressure?, does it change after it's been running a while and getting hot?

Exactly how are you setting the timing?, what distributor do you have?
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[dgwduck]

Thanks for the comments. The cold start is ok all the time now so sorry the confusion was my explanation. I only grounded the temp sensor which cured the no start earlier but now it starts fine hooked up. I believe the dizzy is original to the motor based on the look of it and the vacuum advance seems to work when you blow into it. Since I use the pertronix I have used a timing light to set the timing and do typically run it a little high and have noticed a slight valve noise in the past so slight when I go up hills. The reason I think it is the valves getting noisy is after I have driven the car for 20 minutes or so I hear the rattle noise and then the car loses power and the temp gradually rises and when I press in the clutch I notice the higher idle. I am going to try another coil later this week as my ohm meter test from terminal to terminal was ok but from coil center to terminal was not in range (Bosch coil) Could the coil be getting hot after 20 minutes or so and sending low voltage? I was also going to try another temp sensor and ground the case of it so it should register a different resistance than the one in the motor which would be hotter. Just a thought. The reason I did not feel like the advanced timing was an issue is I have driven it 10,000 miles over the past 3 years running high and not had an issue. Any thoughts?

[busdaddy]

Wow!, "a little higher" huh?, you are a bad bad boy.....

Don't cheat on timing, with both hoses off the distributor it should never ever exceed 32 degrees BTDC regardless of how high you rev the engine. Valves make noise all the time when loose, not just under power, uphill, downhill, idling, etc... You might be hearing detonation, or damaged ring grooves from the 3 years of excessive advance, or even a loose head in a worst case scenario, fingers crossed for you.

A bad coil when hot may cause bucking or quitting, but it won't have anything to do with engine temps. Fuel pressure, vacuum leaks and timing are the principal causes of heat, it's up to you to find out what's not quite right.
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[dgwduck]

Well that is not good news. I will try setting the timing by the book and see what happens. Looks like I might by installing a pairs or heads this winter. Curious if you think the after market heads are ok to use or see if mine are rebuildable or get used vw oem and have them rebuilt. Thanks for your help

[busdaddy]

I don't have much experience with new heads lately, so I can't be much help there, see what your OG ones look like first.
Fingers crossed some timing work, and other adjustments and repairs solve the problem first, no need to go full doom and gloom just yet.
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[Maltboy!]

I'm working on a 76 Super. I think all the wiring is sorted except for one mystery. There are two red/blue wires with clear rectangular covers in the dash.
Both are male. One goes to the double relay, and the other goes to the fuel pump. It looks like they are supposed to be connected somehow, but I don't see any dashboard junctions on the schematics. It looks like this connection is T1D on the schematic, but it says that one is supposed to be in the trunk. That can't be right because both connectors are at the end of the front/rear harnesses where all the other dash wires terminate. Am I missing a double female connector, or do I have something wired wrong?

[MuzzcoVW]

[Gr0unded]

[Maltboy!]

[Gr0unded]

[Maltboy!]

[Maltboy!]

I found this laying on the floorboard. It is exactly what was needed to join the two male fuel pump power connectors. It appears to be factory based on the connector design and crimp quality.