fya32

Hello guys, im new to the forum and hope to get the help from the best out here.

I have a 1976 porsche 2.7 cis with 20,000 miles only that has been sitting for long and did a full top end rebuild with 2.8 sleeves and pistons , engine resealed, valve guide checked and chain tensioner upgraded.. other than that all stock , car have a nice power and smooth driving.

it was all perfect but recently it was acting weird



however, i am having an unsolvable issue regarding the car having hard starting when getting hot to operating temperature, so when the car is cold it starts immediately and stays on 800-900 rpm idle smooth and no smell of fuel or weird smell from the exhaust and also the plugs are burning good so nothing to worry about the air/fuel mixture i guess but after driving it for 20-30 minutes and it gets warm, after shutting it off for +10 minutes it wont start again. it just tries to catch up the start for less then a second then it dies and then it will take 3-4 attempts to start with the gas on the floor for almost 10 seconds every time for her to start and it starts like its flooded or something which is very annoying and also embarrassing honestly.


we replaced the fuel pump and fuel filter, replaced the gas tank , checked the fuel distributor and opened every fuel line on top to see the pressure on every head and replaced all the washers on top , checked the fuel accumulator and if i recall it was good also .. today we found that 2 of the 6 injectors are leaking fuel so my mechanic told me that when you turn the ignition on when cold it should splash fuel to let the car start when cold so it will start up normal right? BUT when the car is driven and you turn off the car, 2 of the injectors will leak drops of fuel and floods the system which will make the car very hard to start again. I am convinced but i dont want to just throw my money on random parts and praying it to be the fix.

so what do you guys think about the leaky injectors? may they be the cause of all this? is there anything i should check or this should be the fix? Thanks.


here are some pics of my car.

theiceman

easy to check ....

so we are assuming it is leak down .. as you have put CIS gauges on and the pressure is not mainted as spec ( not sure what it is but there is documentation on the net.

if you think it is fuel injectors here is what you do ..

drive the car and warm it up or get it hot or whatever...

have 6 small containers like baby food jars or whatever and a set of channel lock pliers.

That car has nylon flexible fuel hoses which is great. After you stop simply grab the injector by the connection and pull them out. it only a rubber oring holding them in .

put each one in a container and watch... if fuel starts t flow out of any of them into the jars, those are your leaking injectors.

but all that said bosch injectors are pretty cheap.

fya32

yes we already checked , we also took it for a shop which specializes in inspecting old mechanical fuel injections and we saw that there are 2 injectors leaking and dropping fuel when you switch them off. but my question is if the problem is this , would changing them fix the hot start issue im having?

systemsc

In the warm start mode, remove the FP fuse before starting. This should help in determining a too rich mixture when warm, e.g. WUR setting off.

J richard

Yes, sticky injectors can cause a hot start issues. Also I would check the cold start valve for leaking as well. Are you sure the accumulator is working properly? Also do you have a pop off valve I the air box? Check to make sure it is seated and not leaking. If you’ve had any backfires lately, pretty common with start issues on cis, make sure the air box is not split and the runners are tight.

fya32

i dont have the pop off valve , i will check those and get back again

theiceman

yes the whole reason it wont start is because the car depends on residual pressure to start hot as there is no cold start assist .
top causes of extended cranking on hot engines are as you notes fuel pressure check valve ( might want to make sure that was replaced when fuel pump was replaced as it bolts right to the fuel pump , ) and accumulator.

If those injectors are leaking and it bleeds off residual pressure.. that is your problem. also keep in mind leaking injectors wash out cylinders so they need replacing anyway .. just buy 6 and be done.

systemsc

So what is it, too much fuel or not enough? The guessing goes on.

fya32

fuel accamulator pressure is low when checking .. its not pressuring enough fuel its just spitting a low amount of fuel

theiceman

you originally said your fuel accumulator is good !!

We can only go on the data you provide .
I think there is enough information in this thread to resolve this unresolvable problem easily.

with a set of CIS gauged measuring residual pressure this car should never leave the shop or a reputable place not working.

good luck.

J richard

^^^^+1 what he said^^^^

fya32

where to find cis gauges?

theiceman

amazon !

J richard

Considering you’ve basically replaced everything in the feel system besides the accumulator and the injectors, and the injectors have been identified as leaking…

those would be the low hanging fruit.

fya32

so i just replaced the fuel accumulator from bosch (not sure about the part number) and bosch coil as well but the problem still there when the car is hot , so in order to start it when hot or warm i have to turn ignition on , remove the air box and put my finger on something like a valve pass until i hear a beeping/buzzing noise and then it starts up immediately..

what i am missing?