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92landyacht · 01-14-2019, 10:55 AM

Correction, mine is a 92 LY but the same engine configuration as the 91 P30.

sraab928 · 01-14-2019, 01:02 PM

Quote:

Originally Posted by Boom Sounds

including all the gaskets on the Rochester 220 and the small hard plastic hose in front of the throttle body.

I did the basic spray around with carb cleaner "test" - not my favorite (due to flammability) but it didn't reveal any obvious leaks.

bkahler · 01-14-2019, 02:38 PM

There is always the possibility that your ECM is damaged in some way. Have you found where the ECM is mounted? There are two parts to the ECM, the main CPU board and the Memcal board. Each will have it's own part number.

In the attached picture you can see my ECM. On the left hand side of the ECM there is a cover that is attached with two small screws. Inside the cover is the Memcal.

If you plan to look for replacements you will need to search for them memcal which will have a part number something like BYYC or BPRK, etc. You can often times find them on ebay. The ECM will have a part number like 16197427. It's my understanding that any ECM with the same number can replace like for like. Same with the Memcal, like for like but I will admit I'm less sure about the Memcal.

Brad

92landyacht · 01-14-2019, 03:11 PM

Quote:

Originally Posted by bkahler

There is always the possibility that your ECM is damaged in some way. Have you found where the ECM is mounted? There are two parts to the ECM, the main CPU board and the Memcal board. Each will have it's own part number.

In the attached picture you can see my ECM. On the left hand side of the ECM there is a cover that is attached with two small screws. Inside the cover is the Memcal.

If you plan to look for replacements you will need to search for them memcal which will have a part number something like BYYC or BPRK, etc. You can often times find them on ebay. The ECM will have a part number like 16197427. It's my understanding that any ECM with the same number can replace like for like. Same with the Memcal, like for like but I will admit I'm less sure about the Memcal.

Brad

The "memcal" is the ROM that contains the calibration data and mappings. It's socketed and may have come loose but not likely. It's also possible that the ECU is damaged but the ROM is still good or visa versa. My shop chose to purchase a combination that was the same as mine to reduce the variables.

Boom Sounds · 01-15-2019, 08:08 AM

See extract from service manual.

sraab928 · 01-15-2019, 09:00 AM

Quote:

Originally Posted by Boom Sounds

See extract from service manual.

Thanks for the info...

I just received my factory service manuals in the mail yesterday - I got the 1991 Truck and The 1991 fuel and emissions factory manuals.

Boom Sounds · 01-15-2019, 12:05 PM

Quote:

Originally Posted by sraab928

Thanks for the info...

I just received my factory service manuals in the mail yesterday - I got the 1991 Truck and The 1991 fuel and emissions factory manuals.

Yup, I think one other which you can get electronically via the links i posted earlier in the thread along with those parts break outs at GMwiki. You clearly have it all covered.

sraab928 · 01-15-2019, 12:45 PM

Quote:

Originally Posted by Boom Sounds

Yup, I think one other which you can get electronically via the links i posted earlier in the thread along with those parts break outs at GMwiki. You clearly have it all covered.

Just enough information to make me dangerous...lol.

Boom Sounds · 01-15-2019, 01:28 PM

Quote:

Originally Posted by sraab928

Just enough information to make me dangerous...lol.

You've become (along with Brad/Chris Craw) a primary target for when I get stuck. I reckon we have a pretty much identical set up. I have the 16" wheels which have different brake codes, other than that, i reckon v similar.

sraab928 · 01-15-2019, 06:30 PM

okay - so I got the tunerpro RT setup tonight - no error codes detected. I took two short videos of it running (and then when it bogs) with two different screens - Ill be honest - I assume when it goes red its bad but beyond that this doesn't mean much to me.... I just did this 15 minutes ago and have done zero research so far... at first I thought coolant temp was odd but its just reading in c and not f -

https://youtu.be/N0U0Qg7kA9M

https://youtu.be/u5P685BV0dk

bkahler · 01-15-2019, 08:12 PM

Can you take more videos with your phone in the landscape mode and also for longer periods? Also take one with no revving of the engine so we can see steady state readings.

Brad

bkahler · 01-15-2019, 08:26 PM

A quick bit of research says maximum advance should be around 38 degrees and you seem be above that.

The spark advance should be controlled by the ecm which tells the distributor what to do.

I'm wondering if your static distributor is really set where you think it is. Have you looked at your crank pulley damper to see if it's in good shape?

I know some types of dampers can slip causing erroneous settings.

Just a thought before going to bed

Brad

Boom Sounds · 01-15-2019, 11:38 PM

Quote:

Originally Posted by bkahler

A quick bit of research says maximum advance should be around 38 degrees and you seem be above that.

The spark advance should be controlled by the ecm which tells the distributor what to do.

I'm wondering if your static distributor is really set where you think it is. Have you looked at your crank pulley damper to see if it's in good shape?

I know some types of dampers can slip causing erroneous settings.

Just a thought before going to bed

Brad

Did you take the tan wire out of sequence when you set your timing?

sraab928 · 01-16-2019, 05:19 AM

Quote:

Originally Posted by bkahler

Can you take more videos with your phone in the landscape mode and also for longer periods? Also take one with no revving of the engine so we can see steady state readings.

Brad

I will do that today and post back.

sraab928 · 01-16-2019, 05:19 AM

Quote:

Originally Posted by Boom Sounds

Did you take the tan wire out of sequence when you set your timing?

Yes I did - and timed it at 4 degrees btdc.

sraab928 · 01-16-2019, 05:22 AM

Quote:

Originally Posted by bkahler

A quick bit of research says maximum advance should be around 38 degrees and you seem be above that.

The spark advance should be controlled by the ecm which tells the distributor what to do.

I'm wondering if your static distributor is really set where you think it is. Have you looked at your crank pulley damper to see if it's in good shape?

I know some types of dampers can slip causing erroneous settings.

Just a thought before going to bed

Brad

It appears in good shape other than normal surface rust - I put white soap in the line and used the lower indicator and cylinder 5 - the motor really runs very well up until the bog.

Today I will retake the videos and check some plugs. Im fighting a finger infection which is slowing me down a little but I think I'm rounding the corner with that.

bkahler · 01-16-2019, 05:44 AM

Thinking it over, there are at least five things that I can think of in the timing arena.

1: Ignition control module
2: Wiring between distributor and ECM
3: ECM
4: ECM spark advance
5: Damper damaged to the point the outside ring has slipped due to rubber fatigue

I'm sure there are other factors as well but these should do for now

Your problem existed before you replaced the distributor so the odds of a new part inside your new distributor causing the exact same problem are pretty slim so I'd say your distributor can be crossed off the list.

Wiring is always a possibility and probably the hardest issue to track down. All I can think of is while you're test running the engine start wiggling connections on all of the instruments, connections, etc to see if anything changes.

I would locate the numbers on the ECM and the Memcal and try and locate replacement parts. I'd suggest ebay as a starting point, that's where I bought my Memcals and ECMs. Prices weren't bad.

Spark advance. This number concerns me the most based on the high spark advance numbers we saw in the video. I believe the ECM assumes a static timing of 4 so no matter where you set the static timing mechanically the ECM will just use 4 as part of its calculation. I saw something like 41 degrees or more spark advance (number turns red) in your video and I'm sure it was displaying red because that's a bad number! It will take some research to try and figure out what sensors and ECM tables contribute to how the ECM determines what spark advance to use.

Damper. I don't know much about GM dampers but on my TR6 and many other vehicles I've seen the damper has a central hub, some sort of ring of rubber and the outer hub. If the rubber deteriorates the outer hub can tear the rubber and slip which would change where the static timing is actually set.

I'll do some poking around to see if I can find out how the ECM calculates spark advance.

Brad

sraab928 · 01-16-2019, 10:05 AM

Okay. So here we go. I seeing some odd numbers for the block learn multiplier. I set out and reset the ecm so I can get new base numbers. She ran a little better but still struggled. I took two plugs out and they looked decent. Not fouled. I then decided not to trust the mechanic and get my own fuel pressure number. As soon as I dropped the filter (which was new when i picked it up) reddish cloudy fuel came out. I decided to put a new filter in and problem solved (for about 5 miles). No back to where I started. Obviously the tank is fuel of trash. Fuel smells good but there must be a layer of junk on the bottom. This would explain the brand new filter and extra new filter in the back storage compartment.

bkahler · 01-16-2019, 10:27 AM

Quote:

Originally Posted by sraab928

Okay. So here we go. I seeing some odd numbers for the block learn multiplier. I set out and reset the ecm so I can get new base numbers. She ran a little better but still struggled. I took two plugs out and they looked decent. Not fouled. I then decided not to trust the mechanic and get my own fuel pressure number. As soon as I dropped the filter (which was new when i picked it up) reddish cloudy fuel came out. I decided to put a new filter in and problem solved (for about 5 miles). No back to where I started. Obviously the tank is fuel of trash. Fuel smells good but there must be a layer of junk on the bottom. This would explain the brand new filter and extra new filter in the back storage compartment.

From what I understand from your description, after replacing the filter everything ran good during your short test run. I'd say you found the culprit. That's good news

Dropping the tank won't be any fun but if it resolves the problem then at least you can move on to other projects.

I'd still like to know why the spark advance number was going so high.....

Brad

sraab928 · 01-16-2019, 06:30 PM

Quote:

Originally Posted by bkahler

From what I understand from your description, after replacing the filter everything ran good during your short test run. I'd say you found the culprit. That's good news

Dropping the tank won't be any fun but if it resolves the problem then at least you can move on to other projects.

I'd still like to know why the spark advance number was going so high.....

Brad

The spark advance issue got better after the ecm reset - Im guessing it had something to do with that block learn multiplier issue. I spoke to a local company that cleans tanks - we are working on a plan to get this tank out and cleaned.