Rebuilt 2.0L FI Type IV, just installed, starts then dies.

timped2006 · Posted: Sun Jul 20, 2014 10:49 pm Post subject:

@Wildthings: That's an interesting thought. I just assumed that everyone's FI bus would run with the AFM unplugged, but it would make sense that it shouldn't. That would also explain the fuel smell and running rich.

I'll add it to my list of things to check this week.

timped2006 · Posted: Mon Jul 21, 2014 11:38 am Post subject:

Potentiometer in the AFM works as it should according to my multimeter.

No change in symptoms with TSII grounded or with AAR unplugged.

I think Wildthings may be on to something with the injectors staying on constantly. I'll check tomorrow to see if a test light flashes or stays on when connected to an injector.

Wildthings · Samba Member Joined: March 13, 2005 Posts: 50350

One lead on the injectors should have fairly constant power, while the other should pulse.

timped2006 · Posted: Tue Jul 22, 2014 10:09 pm Post subject:

Had a little adventure with my multimeter tonight. After considering what Wildthings said about the injectors being always on, I did some reading and attacked the beast with a test light.

Wouldn't you know, all four injector plugs had 12v CONSTANTLY...and at BOTH TERMINALS with the key on. Wildthings, that's why they pay you the big bucks.

Interestingly, that constant power issue went away when all four injector plugs were off, but came back with any one of them plugged in. That's when I decided that the short must not be at one of the plugs, but further upriver.

From there, it was just a matter of tracing the short backwards until I found where the continuity problem stopped.

In the end, I found the resistor pack has infinite continuity at all terminals. There is no resistance between the power supply going in and any of the four wires coming out the ends of the resistors. I thought maybe the hot wire was grounding to the cage, but there's no continuity there. Must just be that the wires are touching past where I can see, or the resistors are all burned up from 35 years.

Cest la vie.

I'll beg, borrow, or steal a new resistor pack and let you know how things turn out. I think I owe you all a beer.

Wildthings · Samba Member Joined: March 13, 2005 Posts: 50350

You need to crank the engine to test the injectors and the ECU. Otherwise you will see 12v on both sides of the injectors just as you did. Pulling the distributor and spinning the shaft will work as well. The key has to be on and ground the coil wire out so you don't shock yourself or start a fire.

Not sure on why you are seeing no resistance through the resister pack. You will see no voltage drop across the resister pack if the engine isn't turning. What range do you have your meter on?

timped2006 · Posted: Tue Jul 22, 2014 10:54 pm Post subject:

Thanks for the heads up. I'll check that first thing tomorrow rather than buy something that might not fix the problem.

So...if the light doesn't flash, that means ECU, right?

timped2006 · Posted: Wed Jul 23, 2014 1:21 pm Post subject:

By the way, I checked for continuity at each injector and it's between 2 and 3 like the Bosch manual says it should be. I think that means I can rule out a short to ground at the injectors.

timped2006 · Posted: Wed Jul 23, 2014 3:24 pm Post subject:

Here are the test results.

All four injector plugs have strobe with the engine running.

Three of the plugs cause the engine RPMs to drop when unplugged. All but #2.

I performed this test with the AFM unplugged so the engine would stay running. I haven't tried with the AFM plugged in because the engine won't run and all this testing has drained my battery enough that I can't get consistent crank. If you think the results with the AFM plugged in would benefit the process, I'll charge the battery for a day and try that.

Otherwise, do these results rule anything out?

timped2006 · Posted: Wed Jul 23, 2014 3:56 pm Post subject:

One more post...I know I've been bombarding you guys.

I just went out and did one more test. With the engine running and the AFM unplugged, instead of plugging the entire plug into the AFM, I just connected the two fuel pump wires on the harness side of the plug. That killed the motor, so I know it's the fuel pump turning on that is flooding and killing my bus. That, coupled with the fact that the RPMs drop when injectors 1, 3, or 4 are unplugged makes me think that they are being held open constantly and, when the fuel pressure increases, those cylinders flood.

I don't think it's the ECU because all four plugs had the strobe effect when checked with a test light with the engine running. My suspicion is that the injectors aren't being closed by the ECU because of a fault in the injectors themselves.

Correct me if I'm wrong.

Is there a way to test the injectors to see if they're allowing themselves to be turned off? I don't think the winding is grounding improperly, because there's 2.7 Ohms of resistance between the injector posts as Bosch recommends.

What else could cause the injectors to stay open even when the ECU tries to close them?

busdaddy · Posted: Wed Jul 23, 2014 4:01 pm Post subject:

Easy enough to pull a couple injectors and stick the ends in baggies and watch for fuel spray when you depress the AFM flap (key on).

Remind me again, were the injectors serviced?
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SGKent · Posted: Wed Jul 23, 2014 4:11 pm Post subject:

please forgive me for butting in. I have to head out the door and don't have time right now to read back thru this.

Be aware that 1976-78 injectors have a ballast resistor block while 1979 doesn't as I recall. I also think that the CA buses had a different double relay number. Be sure these things are taken into account in the testing.
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timped2006 · Posted: Wed Jul 23, 2014 4:32 pm Post subject:

Busdaddy: I'm about to find out if all my problems have just been the result of leaky injectors. Would make sense that the fuel pump sending more fuel to leaky injectors would cause them to leak faster and flood everything. As much as I'll feel like a fool if that's the problem, it'll be a welcome solution.

I'll let you know.

timped2006 · Posted: Wed Jul 23, 2014 4:35 pm Post subject:

And to answer your question, they have not been serviced. I guess the bus dying when I plugged in the AFM sent me straight down the electrical route and I didn't even consider that the injectors could be stuck open or leaking because of a mechanical problem. DOH!

timped2006 · Posted: Wed Jul 23, 2014 5:10 pm Post subject:

The injectors don't spray with the key on and AFM flap open.

busdaddy · Posted: Wed Jul 23, 2014 5:13 pm Post subject:

And you heard the pump running?
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timped2006 · Posted: Wed Jul 23, 2014 5:29 pm Post subject:

Yes, sir. Pump was whirring along. I wasn't turning the engine over, but the pump was running and there was nothing coming out of the injectors. I guess that means no leak.

Why would the RPMs drop when all the other injector plugs are pulled EXCEPT #2?

Wildthings · Samba Member Joined: March 13, 2005 Posts: 50350

busdaddy · Posted: Wed Jul 23, 2014 5:38 pm Post subject:

Interesting, the only explanation I can come up with for no drop on #2 is the injectors are functioning with the gravity feed but #2 may not be, the least of your worries at the moment.

Plese refresh my memory regarding the results of your fuel pressure test, I'm having a hard time juggling the different yet somewhat similar threads Razz

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timped2006 · Posted: Wed Jul 23, 2014 6:09 pm Post subject:

Thanks, Wildthings. That makes sense that they wouldn't be spraying unless the engine is turning.

Busdaddy: Fuel pressure is 40 now with the starter running and 40 with the key on and flap open.

Here's my last post and last test for the night. It's time to let it rest and take the wife to dinner.

I just tried one more time to run the bus then plug in the AFM. This time, however, I held the fuel pump leads apart when plugging it in. The bus still died. So, if I plug in the AFM without the fuel pump, it dies. If I plug in ONLY the fuel pump portion of the AFM, it dies. This leads me to my next suspicion. Maybe there's a big short in the part of the harness that goes to the AFM and when I plug it in, several or all of the wires in the harness are being connected together. Or, it could be that the AFM is bad and everything in the box is grounding when I plug it in. It doesn't seem to matter which part of the plug I put in. I'll be checking continuity between each lead on that part of the harness with where it's supposed to go and making sure it's not going anywhere it shouldn't.

As I stated in my original post, this is a rebuild, so maybe the old wires got broken when the harness was out of the bus and hanging on the wall in my garage.


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Rebuilt 2.0L FI Type IV, just installed, starts then dies.
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