View Full Version : Carburetor on V8 4100 HT Eldorado 1985 ?

09-08-11, 06:11 PM
I have a 1985 Cadillac Eldorado Convertible, I love this car!

But I have a problem with electronic fuel injection which does not want to start on the V8 4100 ht ...:(
there is the spark to the spark plugs, fuel is ok but it does not start.

I have a very good friend who is an excellent mechanic and who offered me to switch the electronics and injection and install a carburetor

he say , with adaptation, it is possible

What do you think? you think it's possible, how can I put on carb?

thank you very much for your help


09-08-11, 07:53 PM
Anything is possible with sufficient time and money. It'd be faster and cheaper to get the FI working

09-08-11, 08:49 PM
The Factory Service Manual has excellent diagnostic flow charts to aid in just this problem. The Fuel Injection in pretty basic. Any good mechanic should be able to track down a no start pretty quickly.
I like to give an engine a quick shot of starting fluid. If the car starts and runs for a second, Then you can assume the ignition system is working. If it doesn't then the problem is in the fuel system.
Pull the codes. Fix anything found. Check the 2 injector fuses. Check for proper fuel pressure. If you do that then you will probably get it to start. It may not run great until you sort everything out but it should start.
Good Luck.

09-09-11, 05:59 AM
Thank's guys for your help!

unfortunately, my control panel to the computer does not work, it remains black, so I do not have access to error codes that could help me find the problem: (

my friend test "the starting fluid" but it did not work ....

I ordered from summit, all of the ignition system, everything is new: 8 spark plug, ignition coil, distributor head, ignition control module etc. .... but it does not work

my friend think it's May Be an electronic failure from the computer who send an bad information to the engine.

as in I'm tired of these electronic failures over again, and repeat the whole system cost me a fortune, that's why I was wondering if an old carburetor could not end my life easier with the insurance to have a car simpler and more reliable for the future

but is that really possible?
That is the Question

I saw on the web, guys install V8 5.7 liters with carb olds in 1985 El Dorado, it works
but on a 4100 v8?

thank's again

09-09-11, 07:52 AM
If starting fluid didn't work and there was no attempted start, Then fuel is not your problem. A Carburettor won't work until you get the ignition system up and running. The ignition system on your car is completely contained in the distributor. The only connection to the on board computer is the spark advance control. This does not even come into play until the engine reaches 400 rpm or more. Until then, the ignition module controls the spark advance with an internal advance curve program. When 400 rpm is reached, The computer sends a signal to the distributor to relinquish spark advance control to the computer.

09-10-11, 05:57 AM
thank's for your help !

we will watch it very closely

09-10-11, 11:22 AM
may be it's the Oil Pump who don't work...we check that !


10-27-11, 09:43 AM
Have you ruled out a failed timing chain gear? rotate the engine to top dead center on the crank pulley and verify the dist. rotor is pointing to number one terminal on the cap. Do this twice to confirm you are on the compression stroke for number one cylinder. you can have spark and fuel but with a slipped timing chain, it wont start. Also, if the oil pressure sender wiring is loose or the sender is faulty, the fuel pump will not turn on.

10-27-11, 04:08 PM
You would be better off if you want to keep the value of your car by not putting a carb on it. If I were you I would fix ther display problem first and then the start and run issue. After all your problem sounds elsewhere besides the fuel. Here is a good place to shop for a FSM.

Bob Tarpenning
10-27-11, 06:23 PM
Go to a salvage yard and get a computer and the module that displays the codes from a wrecked car. I got a computer for my '84 Eldorado convertible from a wrecked '84 Brougham. It had the same computer. Cost $35.00. Works great.
Bob T

01-06-12, 04:11 PM
Thank's a lot Guys !!!

i just received my oil pump and try to install this week end :)

if that's doesn't work, i try to change the timing chain gear !

i tell you the results soon !!

thank's again

01-10-12, 02:13 PM
Hello Guys

Do you know if it is absolutely necessary to remove the engine to change the pump oil?

or is it posssible to change the pump oil from under the Cadillac?
that's what I try to do it but the screws are not easily accesible
: (

thank you for your help!



01-10-12, 10:55 PM
The oil pump won't keep the engine from staring.As long as the engines oil pressure is ok i would not change the pump. The oil pressure switch has a second set of contacts that will shut off the fuel pump if the engine stalls and the oil pressure goes beloe about 5psi. But even if this is bad the car will still start. It will just quit in a few seconds. If the starting fluid made no attempt to start then you have an ignition or ignition timing problem. Make sure the distributor is turning when cranked. These engines have a bad habet of striping the distributor gear. Make sure that you have spark. Make sure that the wires are on in the correct order. Make sure that they are not 180 degrease out of time.Check to make sure that the proper power and ground are at the distributor terminals. An engine needs 3 things in the correct order to run. Ignition, Compression, And Fuel. Starting fluid eliminated fuel as the problem. I assume that you can hear the compression when the engine is cranked over. That leaves Spark.

01-11-12, 04:07 PM
Thank's aeronca

In fact the engine start sometimes and stop.....
often when we moved the head of the dstributor

All the ignition is new, sparks plug, distributor and all the wires,
with my friend mechanic, we can see the fuel by the injectors and we have the "sparks" at the sparks plug.....

so, we think it's maby oil pump or the Timing chain ( but we don't have a noise in the engine so not sure for the Timing chain )

thank's for your help !!!!


01-11-12, 04:44 PM
Verify the #1 cylinder is on the compression stroke and the crank shaft timing marks line up. Then pull the distributor cap and confirm the rotor is pointing at #1 terminal. By moving the distributor, it sounds as if the timing chain has slipped. It wont make any noise because the chain does not break, the nylon teeth on the cam gear do, which allows the chain to slip out of time.

01-13-12, 05:57 PM
I think you have to remove the starter and the right drive axle in order to remove the oil pan.
You say you have fuel and spark but no start?
My 83 has steel timing gears, so it turned out to be a worn out cam shaft causing my issues.
Pull the valve covers, turn over the engine and check the rocker arm motion.
In hindsight I wish I had done that before I spent cash.

01-13-12, 11:29 PM
As I said before, verify the rotor is pointing at #1 cylinder in the dist. cap when the timing marks are aligned. Very simple basic diagnostic step. A flat cam will still allow the car to start.

01-16-12, 04:12 PM
thank's for the advice carnut !

02-26-12, 09:38 AM
Some fresh news :

we change the oil pump and the Eldorado start immediatly !
but after 2-3 miles my Eldo stop again
and don't want to restrart :(

I don't understand, 60% of my car is new parts !!!!

some ideas ?

may be it's the computer who stop my cadillac ?

thank's again

02-26-12, 02:04 PM
You say with a new oil pump it started and ran then stopped.
If you havent already, eliminate the relay with new one. You’ve replaced everything else but the ECM.
Asuming you’ve checked and cleaned the ground connections at the engine.

Go to a salvage yard and get a computer and the module that displays the codes from a wrecked car. I got a computer for my '84 Eldorado convertible from a wrecked '84 Brougham. It had the same computer. Cost $35.00. Works great.
Bob T

While cranking the engine, the ECM requires a minimum oil pressure reading, (about 5psi), from the oil pressure switch before completing the circuit by ground. If the ECM sees no oil pressure it wont complete the ground.

The majority of electrical problims are due to poor ground connections.