audi49

Recently I've noticed that my '88 944 base is very difficult to start if it sits 'too long'. 'Too long' seems to be longer than a week or so.
Otherwise, the car starts right away. When it has trouble starting, it'll take a lot of crank attempts to get it started... like 5 to 10 cranking attempts. But eventually it always starts.
So I suspected a fuel delivery issue, and measured the following:
-Engine stopped and DME relay jumped (fuel pump on): 33 psig (36 +/-3 psig per Clarks Garage)
-Engine at idle: 26 psig (29 +/-3 psig per Clarks Garage)
-With fuel pressure regulator vacuum removed & idle: 33 psig (per Haynes manual should be 33 to 39 psig)
-20 minute leakdown test: 31 psig (14.5 psig per Clarks).

So all of these numbers look 'ok' I think, except maybe the leakdown pressure. Clarks states that if it's significantly below 14.5 psig, then it could be a bad check valve. It does not state whether a significantly higher number like 31 psig is a problem or not. I'd suspect not.

Any feedback would be welcome and perhaps what I should check next.
Thanks.

Chalt

Difficult to start when cold. Have you been to Clark's and followed the troubleshooting? Here --------> TS-01, Engine

Anecdotally, mine was doing what yours is and it was my DME temp sensor. That tells the DME if the engine is cold or hot and adjusts the fueling accordingly. A failing sensor created a lean condition on cold start, very very lean. It was a $20 part that fixed my issue. I had good fuel pressure like you.

I don't recommend rushing out and buying that sensor. Do the troubleshooting and work methodically.

audi49

Will take a look but a cold start 1 day after driving is not an issue. 1 week later it is an issue. So not every cold start is hard starting.

Jfrahm

If you get into the "5-10 attempts" stop after 2-3 and pull the plugs, see if they are wet.
If the plugs look OK when it's cold enough to have trouble starting, give it a shot of starting fluid and see if it starts right up.