77 Bus Injectors Sticking

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dlbass93
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77 Bus Injectors Sticking

Post by dlbass93 » Tue Feb 18, 2020 6:20 pm

Hello everyone!

I have been slowly rescuing a Bus (could be a Champagne I based on Internet findings) that I collected last year sometime. Threads on this site have already saved me loads of headache and needless questions, but I'm really confused on this problem. To keep it brief, I got the Bus in non-running order, and someone was in the process of fitting dual ICTs. Mixed amongst piles of other junk in the Bus, I found all of the original fuel-injection components. I have most of that stuff fitted, but I have tried to ignore the EGR items as the currently fitted and sloppy exhaust has no bung for which they might connect.

The issue I'm seeing is that the Bus will start and run around my back yard wonderfully for days at a time, and then it will begin stuttering, and within minutes will be dead and basically impossible to start afterwards. I have fitted a fuel pressure gauge, and can see the pressure act sporadically while starting, jumping from 0 to ~30psi. If I use a screwdriver to reach into the airflow meter to move the gate by hand, the fuel pressure acts the same. I can disconnect the ECU harness at the ECU, or from all four injectors, and the fuel pressure will immediately achieve ~30psi and remain stable for many minutes. If I disconnected the injectors (and not the harness at the ECU) I can reconnect any one of the injectors and the pressure is lost. If I left all of the injectors connected and disconnected the harness at the ECU, I can connect the ECU and go start the Bus and drive around.

The cold start valve and the thermo time switch are both connected, and appear to be in working order. All of the idle air and bypass air control stuff has not been fitted, and the vacuum ports are plugged with silicone bungs. I've followed the the fuel-injection troubleshooting guide as best I understood it, and when the Bus is working, everything checks out (I suppose that should be obvious to me, but...) and when it isn't working, none of the injector tests work because they always have power (until I 'reset' the ECU by reconnecting its harness).

New parts: (hopefully relevant items only)
  • Fuel pump
  • Fuel filter (second one, first filled with rust, this one is not yet filled with rust)
  • Fuel pressure regulator
  • Fuel hoses
  • Vacuum hoses (only using brake booster and fuel pressure regulator)
  • Intake runner boots
  • Intake manifold gaskets/spacers
  • Fuel injector seals
When I first got the Bus, I removed the engine, and cleaned all the years of gunk off it as best I could without disassembling it past the air cooling system. I fabricated a small block off plate for the EGR valve that was mounted to the intake plenum and carefully tossed the clogged-up valve into a bin for safe-keeping.

Have any of y'all seen anything like this? Do I have a bad ECU or harness?

Jivermo
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Re: 77 Bus Injectors Sticking

Post by Jivermo » Tue Feb 18, 2020 6:53 pm

Congrats on returning to fuel injection! Colin recently showed me how to bench test an injector, using a simple 9V battery. Just BRIEFLY attach 2 jumper wires to the injector, and see if it clicks and/or spits. If so, you’re good. I’d pursue the crud in the gas tank and clogging filter business. Remember Colin’s rugged time with Naranja, when all the old stuff in the gas tank began breaking free, and clogging his filter? A real ordeal. Good luck! Oh, I see you are new...welcome! I’m sure he’ll be weighing in soon.

dlbass93
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Re: 77 Bus Injectors Sticking

Post by dlbass93 » Wed Feb 19, 2020 7:53 am

Hi Jivermo! Thanks for bringing up those two things I forgot to mention in my novella up top.

When I had the engine out, I cleaned and tested each injector, but I used a 12v bench battery I use for things, before I read that the injectors wanted 3v or 5v or whatever. They all seemed to be in great shape, except they wouldn't do much more than drip without some pressure on them, and I never did that step. I just checked for clicky clicky like you suggested and that fuel could get through.

As for the fuel tank, when the engine was out I removed the access panel and was shocked at how spotless everything was in there, so we blew air in the tank and nothing sounded off, and nothing but air blew out, so we did the stupid thing and left the tank alone. After four or five gallons of fuel ran through the filter, it was so red and clogged that fuel would wouldn't even drip through it. I pulled the hose off in front of the filter and drained a gallon out into a jug, and the fuel was perfectly clean. So, I just stuck another filter on, and so far no trouble. I don't recall having read Colin's thread on his fuel tank woes with Naranja, so I'll go find that for reading tonight.

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Amskeptic
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Re: 77 Bus Injectors Sticking

Post by Amskeptic » Wed Feb 19, 2020 9:51 am

dlbass93 wrote:
Wed Feb 19, 2020 7:53 am
Hi Jivermo! Thanks for bringing up those two things I forgot to mention in my novella up top.

When I had the engine out, I cleaned and tested each injector, but I used a 12v bench battery I use for things, before I read that the injectors wanted 3v or 5v or whatever. They all seemed to be in great shape, except they wouldn't do much more than drip without some pressure on them, and I never did that step. I just checked for clicky clicky like you suggested and that fuel could get through.

As for the fuel tank, when the engine was out I removed the access panel and was shocked at how spotless everything was in there, so we blew air in the tank and nothing sounded off, and nothing but air blew out, so we did the stupid thing and left the tank alone. After four or five gallons of fuel ran through the filter, it was so red and clogged that fuel would wouldn't even drip through it. I pulled the hose off in front of the filter and drained a gallon out into a jug, and the fuel was perfectly clean. So, I just stuck another filter on, and so far no trouble. I don't recall having read Colin's thread on his fuel tank woes with Naranja, so I'll go find that for reading tonight.

I think you have a grounding issue.
a) the injectors are supplied with voltage any time the ignition is on.
b) the injectors only spray when the ECU grounds them (we're talking in thousandths of a second)
c) the ECU must have its own ground path to successfully ground the injectors.
d) you must have snug secure tight ground spades at the crankcase! (three wires, two spades)

Make sure that the double relay ground path is secure, and make sure that the engine/transaxle ground strap is secure.
Colin
BobD - 78 Bus . . . 112,660 miles
Chloe - 70 bus . . . 206,845 miles
Naranja - 77 Westy . . . 116,898 miles
Pluck - 1973 Squareback . . . . . . 55,570 miles
Alexus - 91 Lexus LS400 . . . 84,465 miles

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asiab3
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Re: 77 Bus Injectors Sticking

Post by asiab3 » Wed Feb 19, 2020 12:28 pm

Grab a digital voltmeter with a resistance function ("ohms" look like Omega, pardon me if you're already adept at this stuff,) and maybe a helper who can read. If your helper can wiggle the suspected wires while you perform some of the tests, that would be excellent too.

Run through the tests on page 40 of the L-Jet troubleshooting manual:
https://www.thesamba.com/vw/archives/ma ... Manual.pdf

For the record, a '77 Federal wouldn't usually have the "3 and 18/full throttle" test. The Auxiliary air regulator test isn't possible with the printed numbers. Ignore it if the bus idles well when cold for now. If the engine starts and runs, ignore the last three voltmeter tests.

The three wire/two plug grounds by the #3 intake runner, (D, in Colin's list above,) should be gently wiggled when testing anything with pins 5, 16, and 17, the ground pins.

Once you've got that done, let us know if anything looks suspect.
Robbie
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

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Bleyseng
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Re: 77 Bus Injectors Sticking

Post by Bleyseng » Thu Feb 20, 2020 10:26 am

Have you check that the Temp Sensor 2 (cylinder head) is in spec cold and hot?
Geoff
77 Sage Green Westy- CS 2.0L-160,000 miles
70 Ghia vert, black, stock 1600SP,- 139,000 miles,
76 914 2.1L-Nepal Orange- 160,000+ miles
http://bleysengaway.blogspot.com/

dlbass93
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Re: 77 Bus Injectors Sticking

Post by dlbass93 » Thu Feb 20, 2020 10:36 am

Hey guys, thanks for the guidance. I have not checked grounds, Temp Sensor 2, nor read through that L-jet manual. It's Mardi Gras now, so maybe I'll get to try all these things next weekend, and hopefully report back with good news soon.

dlbass93
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Re: 77 Bus Injectors Sticking

Post by dlbass93 » Mon Feb 24, 2020 10:31 am

Grounds
Left side of intake seem good, but I found the double relay harness ground was not tight enough, that's now fixed.

Page 40 in AFC manual
Skipping the ones Robbie mentioned, everything but the two notes below test within specification.

Test pins 6 & 27 Air Sensor Cicruit - max 2800 ohms at 68 F
Result: 2.92 @ 20k resolution and infinite @ 2k resolution
Maybe related to disconnected auxiliary air circuit?

Test pin 13 & ground
Result: infinite resistance
Head temp sensor fails direct lead to shoulder test. Will replace sensor ASAP.

---

Another thing I noticed while reading through the AFC manual is that the bus should have a vacuum advance, but mine does not have vacuum advance. Upon further inspection, it is an 009, and the spare is also an 009.

I have an unknown harness coming from a sensor just inside (right) of the #3 cylinder. Also there are two disconnected wires at the beginning of the ECU harness, they go to pins 9 and 12, but the AFC manual says 9 is in the airflow sensor, and doesn't mention a 12 that I can see. Any ideas?

dlbass93
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Re: 77 Bus Injectors Sticking

Post by dlbass93 » Wed Mar 18, 2020 11:55 am

]Update
The new temp sensor tests exactly the same as the one in the Bus, so I didn't swap it out. I am probably just not using my voltmeter on the correct resolution, as I can get readings closer to spec when setting a resolution manual. I don't recall what setting I used to see a reasonable number.

The good news is that the Bus has not acted rudely since correcting the grounds at the double-relay, so I think you guys solved my issue.

Lots of bodywork to finish up, and maybe it will be on the road sometime this year!

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