start up after a day or two
 

Hi guys,
I have searched but haven't really found a topic that was exactly the same. Here are the details, and any advice or things to check would be greatly appreciated.

The car: 1986 911 coupe, 3.2 unmodified, fresh engine rebuild, top and bottom
what I am going to explain was happening before the rebuild as well and was not the reason for the rebuild, there were some major issues which are now resolved.

When I try to start the car after a day or two of not using it it will crank fine and turn over and start breifly, for about a second then stalls.

I turn the key to off and try again right away, it does the same and fifity percent of the time keeps going, the other fifty percent it stalls once more.

If it stalled the second time I try again and it fires every time, never takes more than three tries and usually only two.

So after the car is started, it idles around 600rpm and is searching quite a bit. I back it out of the garage, it takes about 3000rpm to get it to start to move backwards, and usually stalls when I get in the driveway and put the clutch in, as soon as the clutch goes in it stalls. Then I fire it up again, starts every time from this point but the idle is searching a bit and is around 700rpm. Now I back out of driveway, sometimes when shifting from reverse to 1st it stalls at end of driveway when I push the clutch in, but not always and always starts right up again. Then I drive down the road to the stop sign, put clutch in to to stop and everything is ok, idles fine at 880-900rpm, no searching and everything is good the rest of the day. Well, it does sometimes feel like I am getting a power blip at about 2600-3300rpm across every gear but I digress.

I am assuming that because it did this before the rebuild it must be something that wasn't worked on, so a sensor or something.

I have replaced the fuel filter, dist cap, tried multiple DME relays, fuel filter relay.

I think I read somewhere that when you turn the key to ON position I should hear the fuel pump kick in, if that is the case, I do not, at least from inside the car. Could it be that the pump is on its way out. Anyway, I know this was long and I will be scolded for not using search, but I did search and didn't find the same scenario. Any help would be appreciated.
Thanks

Have you checked your Iidle Control Valve?

First, the fuel pump is not supposed to run with the key to ON. It only runs when you crank or when the flywheel rotates with more than 200RPM. So no worries there.

From what you describe the car might just not be happy when stone cold. This could be why it is not running properly. But once some heat develops in the engine it starts to run fine. The DME uses the CHT to determine engine temperature and enriches the fuel mixture. With no enrichment an engine would be very hard to start when cold.

Maybe your CHT is bad. Check that it is the two-wire version and that it shows the proper resistance according to specifications with the engine cold and with the engine at operating temperature. If the CHT is good it could also be the DME itself not interpreting the CHT signal properly.

Other than that I agree with the previous poster. It could be a sluggish ICV - hard to tell without further diagnostics.

Ingo

A leaky injector will bleed off the pressure in the system.

My injectors should be fine as they were checked and cleaned during the rebuild. I do have the two wire CHT, it was installed by the PO. Is the ICV something I can test myself, same goes for the CHT? If they don't check out is replacing them difficult to do? I have the bentley manual but am new to wrenching. If those two things check out would the next step be having the DME itself looked at? Anyone have one repaired, what type of cost is it? Any recomendations on shop.

Thanks

You'll need a meter, per Bentley, to test the CHT and ICV.

DME checks could be a bit more involved,..start, first with the simplest before heading to the DME.

Keep us posted.

Doyle

Sounds like the CHT to me also.

Ok guys, I have checked the CHT and it is bang on, the ICV checked fine, even tried another one with no luck. Air fuel ratio was .98 now it is set to .90 lambda. Car still works great after I get it running but starting it can be a pain. crank crank crank start, stall. crank, start, sometimes stall sometimes not. Give it a minute and everything is fine. What should I check next

Have you tried to set the idle by jumping out the ICV? Checked the O2 sensor?

One simple thing to check for is moisture in the distributor cap. My dad's 88 will behave just like that when it has moisture in the distributor cap. I usually let it sit open overnight to let it dry out then it is fine. I have since put a smear of silicone grease around the base of the cap and it hasn't happened lately. 3.2's seem to not like moisture in that area.

Probably not the culprit, but it's a simple check/fix.

The dist cap is new and dry as abone but was worth a try thanks. How exactly do I jump the ICV to test the O2 sensor? Thanks guys keep it coming

Your check valve in the fuel pump's outlet may be defective allowing the car to lose the "prime" at the fuel rails.

Fuel pressure checks?

Doyle