911s running rich/ doesn't start when hot

[privatepang]

Hey guys,

Bought a 75 911s a few weeks ago that has been sitting undriven for at least 6 years(indoors) and after i bought it, I sent it to a porsche specialist mechanics for the last few weeks. Its had:

- Gas tank refinished
- New fuel lines installed
- Valve adjustment
- Oil change
- Battery replaced
- Misc work done

Mechanic has got it to a stage where it drives but there are still a couple of issues:

- Spent a bit now getting it to this stage and have been told it'll fail smog here in Vancouver.. Its running rich. Suggested by mechanic that the fuel distributor has to be replaced at a minimum. What other steps can a noobie like me take to test this without outlaying more $$ (gone over my budget at the moment)

- Starts fine when cold but when it does a hot start, I have been told that there is a loss of fuel pressure. Car will eventually start again when it cools down. Now the previous mechanic recommended I get the fuel pump relocated to the front from the rear but my current mechanic did not think this was neccessary. I have done a search here on pelican and have seen that a few people have done this. Could this be a possible reason for this?

Going to take it for the smog in 2 days and even if it fails i can register it for 3 months so i'll probably take that approach while i save up for more work but if there are any recommendations you guys can provide, i'd like to give it a try. Bought this car to up my very basic mechanical skills so I was hoping to DIY as much as possible.

Any ideas would be appreciated. Thanks!

[Sirius Driver]

Its always best to have the CIS system checked but I went through the same thing and spent the money and it paid off. Check for threads or posts that I have logged on here. Cheapest thing to do is to replace the pressure relief valve(i think its called that) at the fuel pump. $5 part btw. The other is to replace the fuel accumulator or FA. This is a $250-350 part that eventually ends up being the problem if the valve was not the problem. Most people will tell ya to get your system checked, and thats sound advice. I was convinced that I had found the most likely of culprits and it boiled down to a Fuel Accumulator which I found at a great price. Good luck.

[tof2.7]

Hi fellow

i have the same problem when i have buy my 74' 2.7, i have change the accumulator but no change , when it's hot no start, i be back to a bhkz and go out the permatune box and it's ok .

start with the accumultaor first !

[privatepang]

Are these things you guys changed yourselves or got a shop to do? Guess i'm in that spot there I want to DIY but at the same time dont want to damage anything as it'll end up costing me more in the long run. I'll look up the accumulator first. Is there a way of checking if its the issue rather than jsut buying a replacement?

[privatepang]

Actually just found your post on replaced the FA. Thanks for that Sirius. Guess i'll have to hunt for one of these and see if its the culprit.

Anyone have ideas on the first issue (running rich)

What are the troubleshooting steps to take? Fuel distributor is between $500 - $1000 so I wanna try as much as I can before looking at replacing this...

[Kemo]

if its running rich hot, have you tried to adjust the A/F ratio when all warmed up? What tools do you have at hand? Its difficult to adjust these cars without the proper equipment.

Having the tools to test the fuel pressure will come in handy. The accumulator is responsible for maintaining a certain pressure in the system, for a certain time, after you shut the car down. From the symptoms listed that would be a good place to look.

[boyt911sc]

Originally Posted by privatepang

Actually just found your post on replaced the FA. Thanks for that Sirius. Guess i'll have to hunt for one of these and see if its the culprit.

Anyone have ideas on the first issue (running rich)

What are the troubleshooting steps to take? Fuel distributor is between $500 - $1000 so I wanna try as much as I can before looking at replacing this...

privategang,

Check your fuel pressures (residual, control and system). If the problem is the fuel pump check valve, or the fuel accumulator, or the fuel distributor, etc. it could be determined without further guesswork. Unless you want to replace each individual CIS components like fuel accumulator without verifying what causes for the fuel pressure loss. While it is very common that the fuel accumulator is the culprit, replacing it without checking the FA is just another guess work. Test and verify, if you care to save your money and time. Every individual CIS components could be bench tested by DIY-ers like you or me including the fuel distributor. If you need further assistance just keep us posted.

Running rich when cold or warm? How did you know it was running rich? Did the mechanic use a gas analyzer to read the exhaust gas?

Tony

[Trackrash]

Are you stuck at Wallmart too?

Stuck at walmart.

[privatepang]

Originally Posted by boyt911sc

privategang,

Check your fuel pressures (residual, control and system). If the problem is the fuel pump check valve, or the fuel accumulator, or the fuel distributor, etc. it could be determined without further guesswork. Unless you want to replace each individual CIS components like fuel accumulator without verifying what causes for the fuel pressure loss. While it is very common that the fuel accumulator is the culprit, replacing it without checking the FA is just another guess work. Test and verify, if you care to save your money and time. Every individual CIS components could be bench tested by DIY-ers like you or me including the fuel distributor. If you need further assistance just keep us posted.

Running rich when cold or warm? How did you know it was running rich? Did the mechanic use a gas analyzer to read the exhaust gas?

Tony

Thanks for the tip Tony. I assume i'll have to get myself a fuel pressure gauge and jsut hook it up between each of these components?

In terms of tools, I need to get a socket set/jack stands. All i have at the moment is a jack. Recently moved to Vancouver so have yet to build up any tools outsdide a standard toolbox

I'll chat to the mechanic when i go get the car this afternoon but yes i believe they used an analyzer. Either way i'll be going to aircare tomorrow to fail it so i'll get a readout there. (allows me to insure it for 3 months at least)

[privatepang]

Originally Posted by Kemo

if its running rich hot, have you tried to adjust the A/F ratio when all warmed up? What tools do you have at hand? Its difficult to adjust these cars without the proper equipment.

Having the tools to test the fuel pressure will come in handy. The accumulator is responsible for maintaining a certain pressure in the system, for a certain time, after you shut the car down. From the symptoms listed that would be a good place to look.

Thanks Kemo. Luckily the accumulator doesnt seem too pricey off pelicans but i'll try the troubleshooting before I change that.

First priority is to get it to pass aircare/smog... Well i asked the mechanic if they can try running it lean for the smog but they said that once its on load, it'll run rich and fail for sure so hopefully get further clarification later today...

[E Sully]

I read your WTB ad for a fuel distributor. I may be wrong, but I believe I read somewhere that if the o ring in the picture is worn it could cause problems with holding fuel pressure. Maybe try cleaning and a new o ring before another fuel distributor?

[privatepang]

Ok. Do u know if this is the only one or are there a few? Appreciate the pics!

[Joe Bob]

Check valve in fuel pump neck.....

Good idea to have CIS gauges to check for hot and cold start fuel pressures....

[privatepang]

Sorry I have 2 threads running where i thought it may have been the fuel pump that had to be relocated but got more info now.

[privatepang]

Sorry had another thread going where i thought it was the fuel pump that had to be relocated but got recommendations to check the FD and possibly clean out the part above.

Ok got a bit more info now.

Brought it back to mechanic again and he did a bit more testing. Theres no external check valve on the pump(aftermarket) and i'll be organising to get one installed however he did a check by turning the car on and then crimping the return fuel lines from the pump to the fuel tank and the pressure from the FD to fuel tank dropped after car was shutdown

He did the opposite as well by crimping the return fuel lines from the FD to the tank and pressure from the FP return line dropped too after shutdown

Only way it would work is if he crimped both return lines to the tank and the pressure would remain (obviously)

So now my next step is to install the check valve on the FP.
He has suggested to replace the FD as it shouldn't be losing pressure.

My question is the check valve mentioned on the FD, is it external or internal? I brought this up with him and he said that its more than just a check valve issue and FD should be replaced.

[Joe Bob]

Stock it goes in the fuel pump neck....as to throwing parts at it. "I" would check the pressures when hot.....

I've NEVER had to move a fuel pump due to "vapor lock".....that's a buncha crap in most CIS hot start cases.

[E Sully]

This is from the CIS manual. It explains the part of the fuel distributor shown in my previous post. It is internal to the fuel distributor, and as mentioned in your second thread on this forum, should be checked. As stated in the last paragraph, it could be causing the loss of system pressure. It is easy to check without taking the fuel distributor apart. If the plunger, part 4, is sticking, or if part 2, o ring seal, is worn it could be causing the problems you have.

[privatepang]

Just to provide an update. Ended up replacing the FD and putting a check valve on the fuel pump and my CIS seems to be working! Warm start is no longer an issue