1979 seville 5.7l. gasoline fuel system

[geody]

My 1979 Seville starts and dies out after 5seconds. it will restart several times before it chugs for a while then runs normally. I have replaced the fuel filter but that didn't help. Any thoughts will be helpful.

[Dave Shepherd]

Lots of issues with that early efi can cause this, coolant temp sensor is the first thing to be checked.  A factory manual is key to owning this car.  The temp sensor can be checked with an ohmeter, off hand I do not have the specs, but we have a real expert on this on the forum. I did plenty of work on these back in the day, but specs are lost to memory. The fast idle plunger/ element was the most common issue of cold start stall. If there is no fast idle when first started that is usually the problem.

[TJ Hopland]

Ya hang in there, Im sure Bruce our expert will be along soon with some things for you to check.

[bcroe]

Good advice, check the EFI coolant sensors, air & water.  They are
interchangeable, both screwed into the intake manifold.  Cold, unplug
them & they should measure in the ballpark of 1000 ohms.  Infinity
means no cold enrichment. 

Those sensors only affect the engine when its cold.  They fail (open
circuit) a lot.  If you only have one good one, make sure its the one
in the coolant, which has far more effect. 

If the sensors are good, the enrichment ckt in the ECU might be bad. 
Easy to check, repair if the ECU is sent here.  The COLD IDLE AIR VALVE
in the throttle body will give you a too fast idle if failed, but will not
affect the fuel mixture. 

good luck, Bruce Roe  CLC # 14630

[Glen]

Bruce,
How does the fuel pump work on these cars?  Some cars I have worked on have a circuit that runs the fuel pump for only a few seconds when the key is turned on.  Then when the engine starts the oil pressure switch turns on the fuel pump for as long as the engine is running.  If the oil pressure switch circuit is bad that would cause the problem geody is having. 

[Dave Shepherd]

That system is not in place on the Seville, they both run key on.

[TJ Hopland]

I believe the relay for the fuel pumps is on the ECU main board and was a common failure point.   I dont remember if it was the connector or the foil to the relay or the relay itself.   I wounder if that could be the issue?  Maybe it starts but then the connector gets hot and the pumps quit?

[bcroe]

I have a drawing on PHOTOBUCKET for the fuel pump circuit.  Check pics 11 & 12,
they are in sub album 70S FUEL INJECTION

http://s93.photobucket.com/albums/l71/bcroe/70s%20FUEL%20INJECTION/

(that is a lower case "L"71, not an upper case "i"71)

  click on a Sub-Album 
  click on a picture to enlarge + explanation

The pumps are supposed to run several seconds with key on, continue if the
engine is turning.  Lots of ECUs I get have failures here.  The relay fails, the
connector or traces burn out; sometimes the in line fuse contacts corrode.  I
believe as the pumps get old, they draw a lot more current.  Then the ECU is
damaged by the current.  I recommend here adding an external relay, so a bad
fuel pump or wiring won't ALSO destroy the ECU. 

A bad integrated circuit in the ECU can also cause the relay to operate, but
that is cheap & easy to fix on a 79.  See the whole circuit on PHOTOBUCKET

     http://s93.photobucket.com/albums/l71/bcroe/

Click sub album 79 ECU SCHEMATIC, mostly pictures 2, 3, & 9.

Bruce Roe  CLC # 14630

[bcroe]

"Click sub album 79 ECU SCHEMATIC, mostly pictures 2, 3, & 9."

Explanation of pumps starts on picture 1.  Bruce