[freddy52]

Hi Friends ! i am the proud owner of 2 extra rare front stretch Eldorado's . 1 was bought in Arizona , and exporrted to France where i live in 2015 and the 2nd one from Germany in 2016 . For both of them , engine is the 350 gas multiport inection from Oldsmobile ( matching numbers with the car )
problem : both of them got the same problem within 2 months : engine stopped when driving , and nothing to do to restart it .
initially , my mechanic thought about injectors , we replaced them , no matter , then fuel pump , we replaced , no matter , then the distributor , replaced but no matter , fuel regulator , no matter ,all spark plugs , no matter same for ignition coil ,spark coil wire , etc , etc , nothing .
Sometimes , at no reason , the engine starts immediatly , runs for a while . but do not restart the next time ! we can try and try untill battery to be empty , nothing !
the problem is that we have exactly the same problem with both of car , that's ununderstandable ! my idea , is that when replacing the distributor ( all new parts from Rockauto ) my mechanic did not respect the procedure , if any .
Is somebody knows how to do ?
with best french regards
frederic

 

[FTSS]

I first thought, "Aha!, they missed ignition coil." Re-read and caught that one. I'm only familiar with the carbed Olds Rocket 350 that was in my '79 Riviera, but the car generally sounds like it's before the days of an ETC sensor (very first hit with outside search: Signs Your Engine Coolant Temperature (ECT) Sensor Is Bad). It provides exactly the same symptoms when it (and/or its wiring connector) goes bad.

After that; grounds. After that; starter. Also too early for oil pressure/level sensors that kill the starting circuit?

Otherwise, you're to be applauded for repping such an iconic manifestation of American automotive kitsch. x2. I've never known about your 'Paris Opera Coupe' conversion, but I saw ads for a stretched hood & shortened rear 2-seater version and have to say yours is much more attractive by comparison. I remember the $40k price, which was some serious coin back then as I had just paid 10% of that for a loaded mint 2-year old '77 LeSabre.

Otherwise, best luck. You'll eventually find someone on here with EXACTLY the fix.

 

[freddy52]

thank you for kind answer , i will transfer all of your recommandations to my mechanic and check all these points . I'll get back soon !

 

[1979 Eldorado]

Hi Frederic,
Before you start replacing everything you should really be guided by the diagnostic trees. There's a very good "Blue" book for the EFI system. It was written prior to 1979 but the system started on the late 1975 Eldorado and the 1976 Seville is essentially the same with some small differences relating to the EGR circuit, fuse position, some wire colors and the ECU map specific to the engine. I will add a capture of the manuals which you should try to obtain. As well there is a Seville org site which has all of the diagnostic trees posted electronically. The link seems to be broken now but I will post in anyway in the event it's fixed:

'76 to '79 Cadillac Seville home page

1976 1977 1978 1979 Cadillac Seville information

www.cadillacseville.org

There is a pair of sensors which measure air and coolant temp. They are identical in PN. Especially the coolant temp sensor is critical regarding starting. If your ambient temp is around 20C, assuming the car is at ambient, the sensors should be reading around 1000 Ohms. Those sensors are very easy to check and should be the first place you start. I am attaching the temp vs resistance chart from the FSM. I make replacements for those sensors. With Covid it can take some time to get them to you but I also have a friend in Poland and he has 3 of my sensors as just in case parts to ship more locally than from the USA.

I cannot go through every possibility but all of the diagnostic tress eventually get down to if nothing else is found the issue is the ECU. There is a member, Bruce Roe, who is extremely skilled with diagnosing and rebuilding the ECU's. So if all else fails you may need to have it checked but there's a lot you can do to diagnose issues prior to changing any parts. I would also consider posting on the CLC website. Bruce "bcore" is more active there.

One other very simple thing to check is the vacuum line going from the car to the ECU. The ECU is located above the passenger foot well. If that vacuum line is leaking the MAP sensor, located inside the ECU, will not get the proper signal. If it's hard or cracked or not sealing well it can be a problem. In all of your efforts did you ever check fuel pressure? The system is as well a 2 pump system. The filter needs to be clean. There's also a small piece of soft fuel line from the in-tank pump to the sending unit and that can deteriorate. It needs to be specifically submersible fuel line. Normal EFI line is not correct for in-tank submerged applications.

Best regards,
Scott

 

[freddy52]

Hi Scott , lot of thanks for all your explainations ! Frederic

 

[freddy52]

hI Guys and Cadillac Owners ! good evening Scott !
back to you as we did all your recommandation without success !!
now , my mechanic is thinking about the ECU , part #16004456 . I cannot explain why , as sometimes engine start and run perfect , and , at the next ignition tes , it refuses starting , even after 100 efforts ? has somebody any idea ??

in the meantime , i wish to all of you my best wishes from France ! Happy new year ....

 

[1979 Eldorado]

Hi Frederic,
The link to the Seville org site is still not working. I do have the "blue book" in the photo but in order to go through it properly we need to know more details...

I'm attaching the index page which shows a list all of the fault trees they include, second a chart which gives the highest probability items according to issue and finally the proper fuel pressure per operating condition chart.

One key thing I'm missing from what you wrote:
-When it starts how long does it run before it stops running and fails to start? Did it already have time to warm-up or is it still cold?
-Were you able to check the fuel pressure while it was running?

The "blue book" is less than 10mm thick so it would ship with little cost to France. I would strongly suggest keeping your eyes open for one on eBay. If you find you need something else and want to group some things I could help you. Anyway let's try to start by defining the issue a little more thoroughly.

It seems strange that both cars do the same thing as well. I did have someone contact me with an issue and based on something I read on the CLC forum I asked him to try gasoline without alcohol. His car would run fine until it was fully warmed and then sometimes it would stall and not start until it was cold again. The theory is the alcohol contain fuel causes the pump to run hotter.

Happy New Year!
Scott

 

[freddy52]

nice to read from you again , Scott ! When the engine starts , it can run as long as we don't stop it ! it can start 10 times in less than 1 second , and sudently , nothing .
yes , all pressure , temperature sensors voltages , everything seems to be correct
as there is no computer on this model , we have no information from the calculator , just the ones you provided in your last answers .
sure , gas pressure is correct , gas regulator valve also delivers the right pressure .

the ECU #16004456 seems to be for a CRUISE CONTROL as i can see on this website : 16004456 | Cruise Control for a Cadillac Eldorado (1979 1980)
i wonder if it would be easier and faster to exit all the injection system , and replace by an good old carburetor !!??

 

[1979 Eldorado]

Once you figure out what's going wrong you will appreciate the EFI I think.

It's still very strange that it runs perfectly as long as you don't turn it off. If the ECU wasn't working correctly I don't think that would be the case. And both cars do the same thing?

The ECU is what reads the input from the EFI sensors, vacuum signal to internal MAP sensor. The system has no O2 sensor and thus it uses a look-up table. If any of the inputs are incorrect then the ECU gives incorrect output.

If it's the ECU then, being in France, I would consider the following:
- 1) Buy a spare ECU from Bruce Roe. Once it arrives replace the original on one of the cars and see if the problem is solved. If it is I would send him your original for repair. You can also try the one he sends you in your second car.
-2) Bruce knows someone in Poland who he has told me is very good with the ECU's. If Bruce can get you in touch with that person it could save you some time getting yours repaired.

Either way I think I would buy at least 1 spare ECU and I would strongly recommend that it comes from Bruce as he has spares which will work in our Eldorados. Bruce is a member of this site but he is more active on the CLC Forum. I will send you a DM/PM with his phone number. My email makes it to him but his emails never make it back to my private email (not in the junk folder either) but they do make it through to my work email.

Scott