Suspected BBi CIS issue

Hi all,

I could use some assistance diagnosing an issue that recently appeared. I suspect that it is CIS related, but I am inexperienced in that area. Maybe someone with more experience could point me in the right direction.

I recently noticed an uneven idle and sluggish acceleration. The car starts fine. The car idles well enough (no obvious issues). With a little throttle, the car feels like it's missing a little (around 2k RPM), and then it's fine again around 2.5k. There is a noticeable smell of unburnt gas, and even low RPM has crackle / burble.

Maybe unrelated, but the exhaust note out the RH side sounds "nice" (choppy rhythm, in a good way, a little higher pitched). The LH side is noticeably smooth (err, boring), and lower in tone.

I used an infrared thermo on each of the exhaust manifold headers. The RH side is 100F+ hotter than the LF side.

Not sure if any of what I mention above is relevant / related, but it's all I have been able to gather at the moment. Figured I'd ask the community before playing detective. My thought was that something was up with the LH side fuel distribution.

Thoughts? Thanks in advance.

 

have a look first at the ignition/distributor cap. easiest and fastest way

 

Thanks, Romano. What would I be looking for? I pulled each plug wire one-by-one, and it appeared they were all sparking. Wasn't sure what to do beyond that (regarding ignition).

 

you have a timing/stroboscope light or may be an oszi? then you can see clearly if the igniton is ok or not.
I think your car has one distributor, one coil? so it happens that the spark in the cap is not always going the right way ( sorry, don´t know how to explain better )
I once had this problem with my BB and sprayed inside the cap isolation spray. this helps for a while. but then had again problems and at night I have seen the sparks at the cap outside. was looking fascinated, but then I replaced the cap and the rotor and all was and still is fine

 

Unfortunately, I've made the situation worse, and the car won't start.

I removed the distributor cap and distributor for inspection / cleaning. I didn't disassemble the distributor / rotor itself. Mostly a bit of Ballistol / electrical contact cleaner (where it seemed appropriate).

After re-installing the distributor / cap, I cannot get the car to start anymore (engine is cranking, but doesn't turn over).

It seems I botched something in my cleaning and/or install. To install the distributor, I aligned the flywheel with TDC (my flywheel has a "1" marked on it). I also aligned the thin rotor arm with the marking on the distributor housing (see attached). I installed the distributor without the cap to make sure the rotor arm didn't move, then installed the cap. It was my understanding that this would mean both the crank and distributor were in sync. Am I mistaken?

Any ideas? I'm at a bit of a loss. Thanks in advance.

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Hi all,

Unfortunately, my problem has surpassed my skill / experience, and so I basically have a very expensive paperweight in my driveway. Speaking of ignorance, I believe I was wrong to think the "1" marked on my flywheel was to mean TDC. Rather, it seems "PM 1-6" is TDC ("Punto Morte" for cylinders 1 and 6")? I manually cranked the engine to the "PM 1-6" hash mark, and reinstalled the distributor (again, aligning the small rotor hand with the marking on the housing). Unfortunately, this did not solve my problem, and the car will not start. Not sure if my incorrect installation prior caused more issues.

If anyone has any suggestions, it'd be much appreciated. Really hoping I didn't turn a minor tuning problem into a much larger (catastrophic) problem.

Thanks in advance.

 

You also need to be at the end of the #1 compression stroke when you set the dist rotor to point at the mark on the dist rim -- you could be off by 1 rev of the crankshaft.

 

Thanks Steve. If I can trouble you for more detail, should set the crank to the "PM 1-6" mark as a starting point (which should the be compression stroke), then offset it based on the end of the stroke? If so, what's the best "crude" way of doing this? The engine is in the car, and I have rudimentary tools. Eg, can I insert a long screw driver in the #1 plug well, manually crank the engine, and wait till the screw driver starts to come back down?

Thanks in advance (get it?!).

 

PM 1-6 is TDC for the cyl 1 and 6, question is only if ignition or overlapping TDC for cyl. 1

can you not see some marks at the camshaft so you see then if igniton TDC or overlapping TDC

for what you want to do this? no reason to do

 

I'm not sure, I wasn't aware this was an option. Can you explain what/how I should go about this? Please pardon my ignorance, I am new to this car, but I promise I'll remember and pay it forward

I guess I misunderstood Steve's comment. Are you both saying that the "PM 1-6" mark is correct, but I have a 50/50 chance of it being cylinder 1, and so I need to reference the camshaft to know whether I am on 1 or 6?

 

but you know how a 4 stroke engine is working? when you not know the basics it makes no sense to explain

correct - so at PM 1-6 the pistons in cyl 1 and 6 are at TDC, but only 1 is ignition TDC, the other overlapping TDC

when you not see a mark on the camshaft then again go to PM 1-6, remove the distributor and turn the shaft 180 °

but all only under the conditon that you have a spark from the coil to the cap. so please check this before all other.

 

Correct. On some models, it's a little easier because you can look in the oil filler cap and see the cyl #1 valves. But no harm in guessing. Just try setting it up on a random PM1-6, and if it won't start, put the flywheel at the other occurrence of PM1-6 where the dist rotor end seems to be 180 deg out from where it should be, remove and reinstall the distributor to line the distributor rotor with the mark, and try that. Alternatively, if you have access to a leakdown tester, the correct occurrence of PM1-6 would be when the leakdown result for cyl #1 is something reasonable (e.g., a few~10%) and not 100% leakage.

 

Okay, thanks guys. This is much appreciated. I will give it a shot tomorrow and report back.

 

So I did as suggested, and that got the car running! To summarize:

1. Bring the flywheel to "PM1 6" (I don't actually see a hyphen).
2. Remove the distributor, align the small rotor arm to the red mark.
3. Reinstalled distributor, then cap (concerned I'd bump the rotor arm if I installed the cap first).
4. Car wouldn't start.
---
5. Repeat step 1.
6. Removed the distributor, and large rotor arm was on red mark. I rotated 180 so small rotor arm was on red mark (per step 2).
7. Repeat step 3.
8. Car starts!

So that was all very helpful, and I learned a few things. Unfortunately, the car's poor idle was not fixed, and has increasingly gotten worse throughout the day. The car appears to be hanging on for dear life. I attached a timing light to each spark plug wire, and I get three strobes, then nothing, then three strobes, then nothing. I attached the timing light to the wire that connects the coil to the distro cap, and I get a burst of light, then nothing, burst of light, then nothing (about 1s on, 1s off).

Any ideas what would cause this? The Digiplex giving up the ghost?

 

You wish that you had Digiplex -- you've got the even flakier Dinoplex. You certainly need to confirm/deny if the ignition system is working well, or not, before worrying about the CIS system. Maybe try a search in this section on "MSD" for the aftermarket system most often used on your model.

 

Robert, a few ideas:

I'm suspecting the timing light. Can you verify it works as expected on another car? On for 1s, off for 1s is very strange. Should be a quick flash only when the spark goes through.

Ballistol does not sound good for the inside of a distributor. If it leaves a residue that may help the spark go where it shouldn't. Perhaps reclean with a pure solvent like throttle body cleaner?

Based on what you said prior to the ignition issues, I suspect a weak fuel pump or clogged filter. The sound of one bank vs the other and the temperature difference of the manifolds point to this since each bank has its own filter and pump.

The CIS tuning is a weird science as you know, I'll leave that option to our experts.

Good luck and keep us posted!

Sent you a PM regarding the 3D scanner thread you made.

 

Ha, oops. I feel like that mixup was made in another post and now I'm doing it. Anyway, I was previously thinking about going with the new MSD Ultra 6A (if / when the Dinoplex failed). I think I'll order one while I continue to investigate. Not super worried about keeping things original (and I can always tuck the MSD box in the old Dinoplex carcass).

 

Yeah, good point. Seemed very odd to me. My other car is a Tesla, so I'll have to ask a neighbor

Hmm. The fact that one bank seemed fine also made me think it was fuel related. Any idea on how to diagnose? Maybe a fuel pressure gauge?

Yeah, not exactly looking for a crash course in CIS just yet. I purchased the books, but I don't have a gas analyzer, etc.. Hoping I can kick that can down the road a bit.

Replying now!

 

Most modern cars don't even have plug wires anymore, direct coil on plug.

Pressure gauge will reveal a weak pump or clogged filter but I can't recall where to tap in easily. Not quite there yet on my build!

A BBi probably requires thousands of times as much maintenance as a Tesla, and they're both fun in their own way. Can't wait until my BBi is driving...

 

Quote| ...Pressure gauge will reveal a weak pump or clogged filter but I can't recall where to tap in easily. ... |Quote

If it is like my '86 Testarossa, you could make an M8 X 1.0 banjo bolt fuel pressure tap for the cold start injector line and either locate it at the injector or at the fuel distributor. EDoug

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Thanks all. I have a few test tools / parts on the way to try and track things down (most gauges / fittings). I am a total CIS noob, but it seems I'll need to learn (I've been reading up!). My plan (unless someone suggests otherwise) is to start with vacuum, then work my way to fuel pressure. There are a handful of places to check. I believe the starting points would be in the primary circuit (blue lines), with many instructions to start with the cold start valve / injector.

The entire LH bank is running poorly, and there is quite a bit of unburnt fuel getting into the exhaust. My guess is it's CIS related, but I'm hoping the vacuum and pressures tests will pinpoint the area.

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We've had over a week of really bad weather here in Miami, so I've had little opportunity to tinker with the car. A few things:

1. The timing light was bad. Got a new one, and it's working as expected.

2. I incorrectly set the timing to "PM 1 6". I don't know how I missed it, but the workshop manual clearly states setting the timing to "AF 18°". The workshop manual appears to cover 365, BB, and BBi, so I am assuming (wrongly?) that the earlier models have the numbers included in the marking. Also, the BBi owner's manual states 10 deg static advance; which I am able to achieve by aligning the distributor when the crank is pointing to "AF". So it seems my timing ignorance / mistakes were recoverable. I also used the timing light on each of the spark plug wires to simply confirm they were sparking (only cyl 1 wire was using for timing...).

3. Despite my misadventures into timing, I am back where I started. Setting timing and cleaning the distributor cap appeared to make no real difference. I may inspect the plugs and regap/replace as another possible solution. Not really what else to consider regarding ignition.

4. I added a fuel pressure gauge between the fuel distributor and warm up regulator. It is showing 70 psi system pressure. I may try another gauge to be sure this is accurate, but it is my understanding (albeit limited) that CIS system pressure should be closer to 80 psi (per 400i manual), or even close to 90 (per the Probst / Bentley book). The lower pressure could result in more a more rich condition, if I understand the way CIS using pressures to lean/rich the ratio. Maybe a blockage upstream (eg, fuel filter and/or accumulator) causing lower pressure downstream?

5. I have a CO analyzer coming tomorrow (doesn't do HC). I'll try to confirm that the car is in-fact running rich, and it's not just my imagination.

Any input would be appreciated.

 

“…4. I added a fuel pressure gauge….”

Only one? I don’t know how bad 70 psi is, but perhaps the other bank has a lower number and is worse. Or are you seeing the same number on both sides? Just noticed you mention the fuel odor from the LH bank. This doesn’t mean bad CIS necessarily, it could still be an ignition miss. How would you know if the extra fuel is from 1 cylinder or 6?

One other idea for a diagnostic tool: thermal camera for the exhaust tubes (depending on their coating or thermal wrap) may show a cylinder missing if one is cooler than the rest. But this would only show you the bad one if the neighbors were good like from bad spark or faulty injector.

You’ve seen spark on each wire from the timing light, but that doesn’t mean spark is jumping at the plug gap where it should. Maybe leaking to ground somewhere prior to the plug gap. To see this you can plot the spark trace on an oscilloscope. I’ll bring one in February when I drive down to the Keys, which guarantees you’ll have it fixed by then!

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I only had enough fittings and copper washers to do the one side. I have some AN fittings on the way, which will allow me to leave an in-line gauge between the distro and WUR (adapting the M8x1 banjo for AN). At that point, I'll have gauges on both sides to see how far out of sync they are.

After I have the gauges in, I was thinking of replacing the fuel filters (was on my TODO list anyway). I think a blocked filter would reduce pressure at the distro, and lead to a rich condition. Not looking to throw random parts at the problem, but it seems this is an easy one.

I initially tried that. It's a little tough to get the same spot on every header tube, so I pointed to the same spot on each of the collectors. The entire LH side is about 100F cooler after warmup, and the exhaust note is much different (calmer). Both collectors on the LH are cooler; which made me think it wasn't any single cylinder because the collectors are 3 cylinders each (might be more than one cylinder, I suppose).

Yeah, good point. I don't have an oscilloscope. I was planning on simply pulling each plug and checking the gaps. Not sure what other "dumb" options I have.

I sure better have this thing running long before then! It is prime driving weather in Miami right now. Definitely stop by though!

Thanks for the help. I'll post back when I've made some progress.

 

No fuel line between the WUR and the fuel distributor is the regulated system pressure.

Referring to the K-Jet without Lambda figure that you posted in Post #21:

1. The green line between the WUR and fuel distributor is the control pressure. Very important, and should be measured both cold and warm. Additionally, you should have a line connecting these two green lines on each bank together so they should always be the same pressure value (however, IIRC, this was a later "refinement" when they got smarter so something you should add if you don't have one -- line #59 here where they use a longer banjo bolt #61 and "stack" two fittings):

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2. The blue lines are the regulated supply fuel pressure which should be the 5 bar-ish pressure number. Probably easiest to measure at the cold start injectors.

3. BBi512 in the US should've been modified to "quasi with Lambda" operation where they add a frequency valve, ECU, and O2 sensor(s) to further alter the control pressure. This can be done incorrectly, or removed incorrectly -- do you have any of this added stuff still present?