76 coupe w/EFI stalling out in +- 30 miles

[CadillacCory]

Hi folks.

I'm new to the club, I got a 76 Coupe Devile with EFI about 2 months ago. I drove it home, a trip of about 850 miles, I did notice it ran a little rough. Upon getting it home I changed the plugs and wires, new fuel filter and took it for a spin, at around 30 miles it suddenly lost power, stopped accelerating, and stalled out.  I waited a while 1/2 hr to an hour and after a few tries I got it to start but it would surge then sputter almost out, surge, sputter all the way to the driveway.  I tried a drive a couple days later same thing.  Thinking it may be a fuel issue, I dropped the tank, had the sending unit rebuilt, installed a new low pressure pump, test drive, same problem!  Replaced the high pressure pump on the frame rail, same result stalled in 26 miles.  Replaced the cap, rotor and ICM, car drove for 77 miles, the Oil pressure light and generator light came on and it stalled out. Has anyone had a problem with a 76 Efi similar to mine or have any idea how to diagnose and fix the problem. Any help would be greatly appreciated!!
Thanks
Steve

[76eldo]

Steve,

It's really important to change the injector O ring seals on these cars.

I am not an FI expert but there will be more responses to your post coming.

The O rings can cause a sudden fuel leak and you will get lots of fuel on your hot engine.  I don't know if the fail in the other way and maybe sucking in air to lean out the fuel mixture.

The other possibility is the ignition parts in the distributor could be failing.  There is a module and a coil in there.

Good Luck,

Brian

[bill06447]

Coil is cheap-give it a try. Also replace the fuel filter if you haven't already-it's on the side of the engine where the fuel pump usually is on the carbureted version.

Bill

[bcroe]

Hi folks.
I'm new to the club, I got a 76 Coupe Devile with EFI about 2 months ago. I drove it home, a trip of about 850 miles, I did notice it ran a little rough. Upon getting it home I changed the plugs and wires, new fuel filter and took it for a spin, at around 30 miles it suddenly lost power, stopped accelerating, and stalled out.  I waited a while 1/2 hr to an hour and after a few tries I got it to start but it would surge then sputter almost out, surge, sputter all the way to the driveway.  I tried a drive a couple days later same thing.  Thinking it may be a fuel issue, I dropped the tank, had the sending unit rebuilt, installed a new low pressure pump, test drive, same problem!  Replaced the high pressure pump on the frame rail, same result stalled in 26 miles.  Replaced the cap, rotor and ICM, car drove for 77 miles, the Oil pressure light and generator light came on and it stalled out. Has anyone had a problem with a 76 Efi similar to mine or have any idea how to diagnose and fix the problem. Any help would be greatly appreciated!!  Thanks  Steve

Steve, I don't believe a slight vacuum leak will have much effect, except perhaps on the
nearby cylinder.  The reason is, the lose of vacuum will be sensed by the MAP sensor and
fuel added to match. So its just like setting the idle higher. 

It seems you have a fuel shortage.  The problem with delivery you seem to have addressed; did
you monitor the fuel pressure?  The other item I use is a wide band OX sensor to tell if the
mixture is rich or lean.  Causes, its either failure of the pumps & injectors to flow the fuel, or
its the pulse width coming from the Engine Control Unit.  Did you say you changed out the
ECU with no change?  These are notorious for failures.  If the internal MAP sensor (an early
rather failure prone design) fails it always cuts your fuel.  There are other parts that can do
that as well.  You can check your MAP, see below. 

Its for sure you'll never get it right unless the ECU is good.  I can test these in about 5
minutes (oh yea, shipping...) and run through anything the engine could do and more. 
The minority that pass ship back for just postage.  Half a hundred 76 ECUs have been
repaired & returned from here. 

There is a blue & white book on these 70s EFIs you might want to have.  On Eb+y all
the time, one is        151743410592   Also read about 70s EFI on my PHOTOBUCKET
first album. 
   http://s93.photobucket.com/albums/L71/bcroe/

  click on an Album
  click on a picture to enlarge + description

BRUCE ROE           CLC tech # 14630                       bcroe@juno.com

[dplotkin]

All well and  good, but his symptoms are consistant with classic HEI ignition module or coil failure. Easy to swap out. I wouldn't expect most fuel problems to wait 30 miles to present themselves, but a sufficiently heated HEI module will do just that. Always check the easy stuff first before condemning a complicated fuel injection system.

Dan

[bcroe]

All well and  good, but his symptoms are consistant with classic HEI ignition module or coil failure.

Always check the easy stuff first before condemning a complicated fuel injection system.
Dan   

Good plan.  Eventually its good to make sure the ECU is OK, before replacing too much. 
Better yet have a spare to swap.  Bruce Roe

[sonny76eldo]

I realize this thread is relatively old, but hope my experience will still find some value.  I have a 76 Eldorado EFI 500 ci convertible which exhibited almost identical issues.  After thorough research (including this forum) the problem ended up being in the HEI system (as dplotkin has pointed out), and I replaced the ignition module which solved the problem.  I also spoke with several individuals from that era, and each one indicated this is an ignition module failure, a common issue occurring when they go bad and get hot.  In my case the car would start just fine when cold, but would stall when hot and under load.  The car had difficulty starting until the engine was cool.

I like the quick, cheap fixes.