Bus is running REALLY rough...double relay the culprit?

[Quadratrückseite]

A couple of weeks ago I had my bus running the best I've heard it run. Yesterday I tried to start it, and it sounds like it is only firing on a couple of cylinders. I have to push on the gas pedal just to start it. While it was (barely) running, I pulled the plug wires from the distributor and it made no change to the engine sound on a couple of them, so I know that at least two cylinders weren't firing. I had spark on all cylinders.

Then after I shut off the bus, I could hear the fuel pump still running - with no key in the ignition. I read about this problem, and they recommended to see if the double relay is the culprit, tap on it with a screwdriver. So I did that, and the fuel pump stopped running. Something about the contacts sticking inside I believe. Do you think that the double relay could be causing the other problems as well?

[dtrumbo]

The double relay can't discriminate between cylinders. All it does is provide power to the fuel pump. Go or no go.

Did you do anything to the bus between the last-known good condition and yesterday when the symptoms appeared? I'd double-check all of the electrical connections (AFM, coil, ECU, etc.) and also all of the vacuum hoses as well. Not to muddy the water, but in my case my weak coil would still show spark between the distributor cap and the individually unplugged plug wires but still not provide a strong enough spark for all cylinders to run smoothly.

[Quadratrückseite]

The double relay can't discriminate between cylinders. All it does is provide power to the fuel pump. Go or no go.

Did you do anything to the bus between the last-known good condition and yesterday when the symptoms appeared? I'd double-check all of the electrical connections (AFM, coil, ECU, etc.) and also all of the vacuum hoses as well. Not to muddy the water, but in my case my weak coil would still show spark between the distributor cap and the individually unplugged plug wires but still not provide a strong enough spark for all cylinders to run smoothly.

As far as I can remember all I did before yesterday and the last time was I unhooked the positive cable to the battery. I did have a vacuum hose that popped off the last time (before I got it running great) but that's back on now. Interesting about the coil - the one that is on there is non-Bosch, and I've always wondered about it. I will double-check all the electrical connections and vacuum hoses. I did notice the top of the AFM cover was off, but I didn't do anything with it. I think it may have vibrated off (Colin and I had removed it on some previous visit and reattached it with RTV sealant)

I do think something is screwed up with the double relay because of the fuel pump running without the key being in the ignition...and then it shuts off when I tap the outside of the double relay with a screwdriver..

[vdubyah73]

you could hot wire the pump, if it starts and runs fine, there's yer answer. try again without hot wire, if it doesn't wanna yer answer has been verified.
has it sputtered or popped back into the intake lately? missfire on same side? either one may indicate vacuum leak. if your afm were a little rich and you had a developing vacuum leak, it would run great. with vim and vigor.
harley guys don't like it when their engines start ''runnin' like a raped ape''. they go looking for a vacuum leak.

[yondermtn]

I had similar symptoms.

Pump continued to run with engine off and key out.

Bus ran really rough


It ended up that a wire came disconnected at the starter. I think it was a FI wire, I forget now.

[Amskeptic]

I do think something is screwed up with the double relay because of the fuel pump running without the key being in the ignition...and then it shuts off when I tap the outside of the double relay with a screwdriver..

Nope. Let's be more focused, shall we? OK where was I, oh yeah, focus.

Turn on the ignition.
Fuel pump on?

Don't tap nothin.

Go to AFM box.

There are little safety contacts on the right that shut the pump off when the engine stops. See if the little silver wire thing has opened the contacts. You can carefully bend that silver wire to get the points opened 1/8" when engine is off.

IF the points are open (!) and the pump is running, unplug the AFM. Pump still running? Pull the LEFT connector off the double relay.
Pump still running? Someone has wired that thing all who knows how.


Colin

[vdubyah73]

so if you unplug the pump and hot wire it and it runs fine and then you disconnect the the hot wire and plug it back in and it doesn't run fine, youve eliminated the pump as the problem.

[DjEep]

The fuel pump should gets power from one source, the dbl relay. The double relay is triggered via the starter (smallest wire on the starter) or the points in the AFM that Colin was describing. If the wire on the starter is attached to it's spade, and the points in the AFM open when the engine isn't turning, the relay is the likely culprit, as far as fuel pump run-on is concerned, assuming the wiring isn't completely hacked.

As for the two cylinder running, assuming it's two cylinders on the same side, check the injector connections, the three FI harness grounds to the case under the intake plenum, ignition components and as stated before, vac leaks at the head, in that order.

[Quadratrückseite]

I did a quick check tonight. The cylinders not firing are 1 and 3. The AFM appears to be working the way it should - the pump comes on when I move the wiper and shuts off when it hits the contact. I unplugged the wiring to the double relay and replugged it in. It started (roughly) and ran with giving it gas. It dies without the gas pedal depressed. Then the fuel pump started coming on again after the engine had died (but not right after the first time it died...it took a few times) The only way I could get the pump to stop running was to tap the double relay, and it always stops on the first tap. I didn't see any obvious vacuum leaks. I still need to check the starter to see if the wire is attached.

[chitwnvw]

The fuel injection chapter of the Bentley has a nice work through of all the FI components, wouldn't hurt to run through it and see if you can narrow down the possibilities.

[vdubyah73]

look at fuel line between tank and fuel rail for kinks, pinches and dry rot. i've seen one way leaks in rotten lines. pump sucks air but line doesn't leak gas....yet.

vacuum leaks, spray a can of carb cleaner at manifold to head joints, particularly the #'s 1 and 3 ports. check s boot, aar elbow, all vacuum ports and lines. any change in engine behaviour when spraying indicates further investigation of area sprayed. let carb cleaner dissipate before spraying at next area. otherwise it's a scatter gun vs marksman approach. take a look at valve cover gaskets as well. if you have annoying drips a v/c, when parked, or you find gaskets out of place, kinda sucked into the head, you have a vacuum leak. crankcase ventilation can get pretty strong. see below.

electrical testing of fi. you're gonna need help from colin or dj. i had dual weber icts in '06-'07. in '08 i gathered all the parts, i had none, an put fi back in. never was able to get it right. went back to the webers a year or 2 later. i like them, rock solid reliable. the reason i couldn't get it right was v/c gasket vacuum leak. as soon as i started it with carbs, oil started steadily running out of my 1-2 v/c. i knew immediately why i was never able to get it right. who'd a thunk vacuum leak through a v/c gasket.

[chitwnvw]

....who'd a thunk vacuum leak through a v/c gasket.

That's good advice, Bill. I've also seen the oil filler tube cause issues...

[Amskeptic]

I did a quick check tonight. The cylinders not firing are 1 and 3. The AFM appears to be working the way it should - the pump comes on when I move the wiper and shuts off when it hits the contact. I unplugged the wiring to the double relay and replugged it in. It started (roughly) and ran with giving it gas. It dies without the gas pedal depressed. Then the fuel pump started coming on again after the engine had died (but not right after the first time it died...it took a few times) The only way I could get the pump to stop running was to tap the double relay, and it always stops on the first tap. I didn't see any obvious vacuum leaks. I still need to check the starter to see if the wire is attached.

One and three. The only thing they share are camshaft lobes. I think your double relay may have a problem. If the starter wire (red/white cold start power) is on the wrong terminal at the starter solenoid, I have heard of diodes blowing in the double relay. You aren't even supposed to have a "wrong terminal" on Bosch starters. So a question here is, do you have a nice original starter, or has it been replaced recently or otherwise. The terminal issue is this, on our starters both push-on terminals are supposed to de-energize when the starter event is over. IF one of those two terminals is live, that kills the diode in the double relay.

Your poor running issues might . . . be downstream of your electrical issues. I would next do a valve adjustment and compression test if you have#1 and #3 issues past the double relay.
Colin
( p.s. the double relay must be well grounded through the brown wire that is under one of the screws that holds the double relay and the series resistors to the firewall/bulkhead)
Colin

[DjEep]

Flat cam perhaps? The 1-3 exhaust lobe likes to go flat on those 2liters, since it's farthest from the thrust bearing and gear, so more prone to wobbling. And an exhaust lobe going flat will often first make it feel zippier before it goes, as it boosts back pressure.

Pull the valve covers and crank it over, coil unplugged, looking to see if the rockers on 1-3 are doing their thing.

[bretski]

( p.s. the double relay must be well grounded through the brown wire that is under one of the screws that holds the double relay and the series resistors to the firewall/bulkhead)
Colin

In case you missed this one...please read it again, Steve. Several years ago, after going through countless diagnostics, I was convinced that I had a faulty double-relay. Bought a new one, and when I took the old one off, I noticed that this ground was not well connected. Lo and behold, that was the root of my problems.

Ever since, my mantra with the FI system has been "Check grounds first, check grounds first, check grounds first." Tapping the relay like you have been doing may have seated the ground momentarily.

Good luck, mi amigo. Get that bus on the road, and let's go camping!