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1976 EFI Fuel Pressure Regulator

Started by Joe Albanese, January 15, 2019, 12:50:34 PM

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Joe Albanese

On a COLD start-up my 1976 EFI Eldo starts and runs fine thru the entire drive regardless of length of trip.  However, when I stop engine and return after about a 20 minute duration, upon trying to start, the engine "rolls" on idle and sometimes will stall out.  If the engine doesn't stall out, eventually after about (1) minute, the "rolling" of slow to a faster idle will correct itself, and the Eldo drives fine once again.
Last night I disconnected the Fuel Pressure Regulator vacuum hose while it was hunting for correct idle speed, plugged vacuum line and it immediately ran like a champ. More acceleration power, no idle "rolling" and even shifts better.
Problem is I have read that you are NOT suppose to disconnect pressure regulator.
What gives here???  Anyone else experience this condition?
Joe Albanese

bcroe

Quote from: Joe AlbaneseOn a COLD start-up my 1976 EFI Eldo starts and runs fine thru the entire drive regardless of length of trip.  However, when I stop engine and return after about a 20 minute duration, upon trying to start, the engine "rolls" on idle and sometimes will stall out.  If the engine doesn't stall out, eventually after about (1) minute, the "rolling" of slow to a faster idle will correct itself, and the Eldo drives fine once again.

Last night I disconnected the Fuel Pressure Regulator vacuum hose while it was hunting for correct idle speed, plugged vacuum line and it immediately ran like a champ. More acceleration power, no idle "rolling" and even shifts better.
Problem is I have read that you are NOT suppose to disconnect pressure regulator.
What gives here???  Anyone else experience this condition?

Disconnecting the vacuum hose will make the mixture richer, esp
at high vacuum.  Could be its a bit lean?  First check that both 2
wire temp sensors are good, about 1000 ohms cold.  After that the
MAP is suspect.  My notes say you have a 500 ECU and a 425 ECU
retuned for a 500, one has a new MAP. Do they both do this? 
Bruce Roe

Joe Albanese

Hi Bruce.  I reinstalled the ECU for the 500 after you shipped it back.  So, I'm running on the proper ECU.  I'm in Florida and don't have access to the other ECU you checked out for me.  So... I doubt it's ECU related.  Another interesting condition is that with fast idle valve completely closed and throttle body air adjustment closed there is still vacuum draw and air flow thru front port that should be closed off.  RPMs are slightly higher than what I would like, yet the only vacuum line that when closed slowed the engine more was the hose to the PCV valve.  Yet PCV valve functions properly when hose is reattached.  Is manifold gas supposed to be brought back into intake air along with fresh air thru breather?  How else can I slow engine idle thru air reduction?  Thanks. Joe A.
Joe Albanese

bcroe

If idle is too high, air must be leaking in somewhere.  I always carry
my spare ECU just in case.  Bruce Roe

79 Eldorado

Joe,
Bruce knows a lot better than I do what the ECU is doing with the vacuum signal but when I initially read what you wrote it reminded me of trying to start a carbureted car which flooded. If you put the pedal of a flooded carb to the floor and keep it there the engine will get more air and it eventually starts but it takes some time, after starting, before the RPM actually comes up despite having the pedal to the floor.

So where am I going with this line of thinking? The values you gave for your coolant/air sensors in your older post did not make sense. The values were really strange. Some time after that old post I tested my air sensor and it was well below the accepted resistance; about 40% lower than it should have been. From what Bruce has mentioned and what I gathered is they normally fail "open" or infinite resistance. That's what my coolant sensor did. My air temp sensor however must have some shorted coils inside because it reads unusually low. I didn't try to find your old topic but when I measured mine I thought possibly yours could be reading very low resistance. What that would do is tell the ECU to enrich the mixture even at high temps where there should be no enrichment. I don't know if it could enrich it so much that the car could act like it's flooded and be hard to start but one way to tell would be to unplug your temp sensors to see if it starts. You would want to repeat the condition and not try this "after-the-fact" because if it did flood unplugging would not eliminate the excess fuel from when you tried to start it.

That's just another thought. It may not hold water but it's certainly easy to check and it gives you another opportunity to get proper readings from the temp sensors.

Good luck,
Scott

Joe Albanese

Scott,
Your analogy seems to hold credence.  I need to once again check Ohms within both sensors - air and coolant - it's just that I'm traveling and don't have access to my tester.  I'm really suspect of these sensors, and no doubt that is the problem (or a part of it).  I did recheck the fast idle valve and it seems to be adjusted properly.  On a cold start, prior to fast idle valve heating up, If I manually depress the valve it will stall out the engine.  Once on a hot engine condition, there is no change to idle and no room to manually depress the valve to make any reduction in engine idle.  At this moment, I have reattached the vacuum to the fuel pressure regulator and I'm learning to live with the idle "roll" for a few moments until I get back to Ohio to check further.  I hate to just start changing out sensors as they are not cheap.  Thanks for your input.  Joe A.
Joe Albanese

79 Eldorado

Joe,
To me it sounds like the fast idle valve is working properly (based on what I've read). I wouldn't recommend throwing parts at it with respect to the sensors because they can easily be checked once you have your multi-meter.

I've been working on a replacement sensor and have one with the exception of a true molded connector. I have been testing the geometry with 3D printed TPU (rubber printable material) connectors however and although the 3D printed ones look a little rough in the back of the center ring with the locator tab the actual functional interface is quite good. I plan to use the 3D printed connectors on my car. The sensing device matches the original quite well and I've tried to select every component to be based on the best durability I could find. If you end-up finding out yours need replacement I listed mine at what it looked like the normal price was before the supply was exhausted and the prices inflated. I wanted to as well offer them as a pair at a discount but I couldn't easily figure out how to do it on eBay with a fixed price sale. My car is stored in the winter and you are obviously able to drive yours more being in Florida. If you find that yours might be part of the problem send me a PM on this site.

Here's a link to the investigation which has culminated in building some first parts. The latest ones look a little better than the one I showed but really the interface part on even the one shown there is not bad. I'm still working on a molding options as well.
http://forums.cadillaclasalleclub.org/index.php?topic=152760.0

Scott

Phil Weber

Scott

The replacement connectors are available at www.ittcannon.com
Check my part numbers but I think the following are correct.
Just google any of these numbers and it will lead you to the website
male boot # 120-8552-000
female boot # 120-8551-000
pin # 330-8672-100
socket # 031-8703-100

Phil


bcroe

#8
Quote from: Phil WeberScott

The replacement connectors are available at www.ittcannon.com
Check my part numbers but I think the following are correct.
Just google any of these numbers and it will lead you to the website
male boot # 120-8552-000
female boot # 120-8551-000
pin # 330-8672-100
socket # 031-8703-100

Phil 

Nice work/research!! 

Check Digi-Key Electronics  for stock.  Bruce Roe

79 Eldorado

Quote from: Phil Weber on January 22, 2019, 04:03:33 AM
Scott

The replacement connectors are available at www.ittcannon.com
Check my part numbers but I think the following are correct.
Just google any of these numbers and it will lead you to the website
male boot # 120-8552-000
female boot # 120-8551-000
pin # 330-8672-100
socket # 031-8703-100

Phil

Wow! I searched "everywhere" and never saw any pictures. Where did you get the PNs and/or how did you know the name? I just did a Google search for images of the one you mentioned and you are correct spot-on. Crazy too because this weekend I just designed the wiring harness half. My wiring harness side was very brittle and started to break. Ok I need to see what the options are for buying them....

Thanks Phil!
Scott

bcroe

#10
I have accounts with Mouser and Digikey, maybe I can get some
sent direct to you?  Not super cheap, how about 5 connectors
and 10 of each contact for openers?  We do not need both
connectors, just the sensor side (which is that?).  Bruce Roe

79 Eldorado

Thanks Bruce. Just before seeing your response I bought some on Mouser to try out. I probably should have checked a couple of sites but Mouser has been very good to work with. Interestingly a few weeks ago I sent Mouser some pictures and a drawing and their tech didn't recognize the connector.

My friend printed the female side which I modeled this weekend and it did turn out quite nicely. I bought a couple to see but I'm ok with the 3D printed version in my car as well.

Scott

79 Eldorado

Quote from: Phil Weber on January 22, 2019, 04:03:33 AM
Scott

The replacement connectors are available at www.ittcannon.com
Check my part numbers but I think the following are correct.
Just google any of these numbers and it will lead you to the website
male boot # 120-8552-000
female boot # 120-8551-000
pin # 330-8672-100
socket # 031-8703-100

Phil

Phil,
It looks like there is a visually VERY similar "mini" Sureseal. It looks like your connector PNs are good but the pin and socket unfortunately seem to be for the "mini" version. The dimensions in the catalog I finally found are not really clear but I think the correct PNs may have "000" suffix instead of "100".

To add to the confusion pn the plugs themselves there seem to be separate PNs for RoHS compliant versions.

Scott
PS: I will also post the same information on my thread to hopefully caution people to check the pin and socket...