EJZero1

Did a good amount of searching the forums, and couldn't find a match to my symptoms...

86 951 with no major mods

Car has become difficult to start unless it has sit for more than a day. If it has sit for a couple of days, it will crank right up.

When symptoms are present, the starter will spin strong for 10-15 seconds and then the engine will start to fire, seemingly 1 cylinder at a time. When starting under these conditions, the smell of fuel is often present. No visible evidence of fuel leaks anywhere.

Have tested fuel system with a gauge at the rail, per Clark's Garage. Idle's at the appropriate pressure, but will not hold any pressure as soon as the engine is turned off....drops immediately to 0.

Fuel delivery issue? I was initially thinking fuel pump return check valve, but why would it readily start after sitting for a couple of days then?

Any additional trouble shooting suggestions would be appreciated.

Dave W.

Maybe an injector is stuck open? That would explain the fuel pressure dropping, and it might take a few days for the fuel to evaporate out of the cylinder. I'd remove the spark plugs, grab a flashlight and look into each cylinder. Normally the piston tops are dry black carbon.

EJZero1

The issue persists.

Pulled the injectors and had them pressure and flow tested at a local shop. All held pressure with no leaks and demonstrated excellent spray patterns. All yielded identical flow volume. So I think I can rule out injector problems.

Duplicated the problem today in the garage and verified spark during the no-start behavior. Great spark at the coil. New distributor, cap, plugs and wires late last year.

Sounds like it must be a fuel issue? But only when warm/hot?

Already replaced FPR when pressure spiked over 100 psi last year. Idle pressure now spot-on according to Clark's Garage, but still immediately drops to zero when turned off.

Fuel back flow check valve? But why would it readily start right up on a cold start after sitting for a couple days?

Fuel pump affected by heat? It'll still start when it's hot/warm, it just has to crank for 15-20 seconds before slowly firing up.

Pressure Damper? Haven't replaced it yet. Would a failing damper resent with my symptoms?

My head hurts. Suggestions for direction greatly appreciated.

83 944

im going through a similarish issue. my 951 with start and run perfect after a few days of sitting and then it will die after 10 mins or so then with fire back up but run rough and as soon as think or touching that throttle it dies. any throttle response and dies.

check for vacuum leaks and does the car stumble then die or immediately shuts off? the fuel smell is probably because you arent burning it. check your speed and reference ohm reading when the problem happens and its possible its the fuel pump. the pump may have the pressure but may not have the volume

mike

mahoney944

Replace the DME temp sensor. Our cars have two temp sensors, one for the gauge and one the DME reads for proper fuel and are on a cold or warm start

EJZero1

Mine never dies once running, just a hard start unless it has sat for at least 24 hrs. Going to start with the most likely culprits that are due for replacement anyway...FPR and Damper. I replaced the FPR earlier this year, but with another used unit, so who knows. Following my only real lead in that my fuel pressure immediately drops to zero after turn off. Pressure/fuel has to be going somewhere...

Will update as soon as I have anything worthy of updating...

adrial

That is a good lead to chase... any fuel in the vacuum line to the FPR?

A little FPR summary ... http://www.ericthecarguy.com/faq/sol...issues?start=5

EJZero1

Thanks for the link ^!

Will isolate the fuel rail as described in the link and see if the pressure still falls away immediately. That should further focus my efforts on the FPR or damper. As indicated earlier, all injectors check out perfect.

Didn't notice any fuel in the vacuum lines when I pulled the injectors for the test last week.

The search continues...