I posted a week ago and new things have developed, so here I go again.

'95, 5.8L, in an E350. auto.

This won't start without starting fluid. A couple weeks ago it ran perfect.

I have fuel and plenty of pressure. (eliminated that problem).

It idles at 2500 rpm, so I disconnected the electric hook up to the 'idle valve'? Once I get it started it idles smooth at 800rpm. It runs great with good power, but not as much as before.

Once it's running I can seal off the throttle body with rubber caps and it still runs! I suspect a vacuum leak somewhere, but I'm getting 21# vacuum on my guage. (OK, I know it's inches of mercury, but it correspondes to the 21# on the guage... I'm getting good vacuum).

I disconnected a spark plug wire and shorted it out. First revoluton nothing..2nd rev, a weak spark, then a hot spark and the engine starts.

I'm starting to suspect a weak electrical system. A weak spark will fire the starting fluid mix, but not the regular mix. Once I get a hot spark everything is fine.

Where do I begin? What do I replace? Going to start with the plugs. This has a distributor cap. Wires and cap look good.

Thanks

 

Possibly a failing EEC relay? What is the primary voltage to the coil during the no start situation?

 

Sounds like you have a very lean condition and that is why it will start with starting fluid.
You have a major vacuum leak.
Things to look for:
1. EGR valve stuck open.
2. Brake Booster line off or ruptured diaphragm inside it.
3. Vacuum line off or broken.
4. Intake Manifold gasket leak.

I do not think you have an electrical ignition problem.

 

checked the ERG. it's ok.

vacuum line to brake booster is where I'm taking my measurements. With the engine off the booster 'inhales' when I remove the line, so there's a good sels there.

Can't find any broken vacuum lines, but still looking. intake manifold leak is my next test. really tough to get at. going to try testing it tomorrow with a real long spray tube and starting fluid.