How To Test A Fuel Accumulator?

[smestas]

Is there a way to test my fuel accumulator to see if it is going bad?

I've recently been hunting a starting problem and would like to see if this part is the cause.

[cmonref]

A bad accumulator will leak from the bottom fitting. The top fitting is hooked to the pressure system of the CIS, and pressure is maintained after shutdown by a diaphram and spring. A good accumulator will not leak from the bottom fitting since the diaphram is not leaking. If the diaphram leaks, fuel will steadily drip from the bottom fitting until the pressure is relieved. (The hose connected to the bottom fitting is a return to the tank.)

[smestas]

Thanks for the reply Brian.

So I should disconnect the lower conection and look for any leaking or driping? Should I do this with the key on/off? After running or when the motor has been setting?

Thanks Again

[Gunter]

Hot or cold start problems? If hot, it could be the check valve on the fuel pump or the accumulator. Start the engine to get pressure in the CIS, stop the engine, then open the bottom fitting to see if there is a leak thru the diaphram. Counter-hold the accumulator with a second wrench to prevent twisting the fitting.

[smestas]

Thanks Gunter.

It always acts up when cold but occasionally when warm as well.

[smestas]

I have to admit that the way I have been starting the car is as follows.

I crank the car over and over repetitively and if she doesn’t fire up I open the deck lid and the air box cover to give the distributor plate a lil lift. Once I hear a bit of fuel coming out I try to fire the motor up again and like a charm she fires right up.

I've been doing this since the motors rebuild 800 miles ago and have already replaced the WUR thinking that was the culprit.

[Gunter]

On the '80 SC, I have a cold start valve. I am not sure about the '78-'79 years for cold start. What gives extra fuel for cold start on those years?

[Oracle]

Originally posted by smestas
I have to admit that the way I have been starting the car is as follows.

I crank the car over and over repetitively and if she doesn’t fire up I open the deck lid and the air box cover to give the distributor plate a lil lift. Once I hear a bit of fuel coming out I try to fire the motor up again and like a charm she fires right up.

I've been doing this since the motors rebuild 800 miles ago and have already replaced the WUR thinking that was the culprit.

I think you're after the 'vapor lock' problem, search like that and you'll find way more information than you ever wanted to know..
-J

[smestas]

Originally posted by Oracle
I think you're after the 'vapor lock' problem

I sure hope it is a vapor lock problem. Because a check valve is a heck of alot cheaper then a new fuel accumulator.

[warpspd]

I have a good used fuel accumlator that I would let
go for $15

[smestas]

Thanks for the great offer Ryan!

I'll let you know in a day or so after I test the one I have.

[Tim Hancock]

You said it happens when cold mostly. The fact that you preload fuel by moving the airplate by hand and then it starts (keeping in mind this is a cold engine) tells me that your cold start valve is not functioning. It is basically an extra fuel injector located behind your airbox/throttle body assy. I do not have a book in front of me right now but basically it turns on and sprays extra fuel into the intake every time you operate your starter (unless the engine is very hot). It gets it's power (do not quote me on this) by receiving a ground signal from a thermovalve mounted on the left chainbox cover which gets its signal from the starter circuit.
When the current flows to the starter it also goes to the thermoswitch and heats a bimetallic strip which actuates a contact that provides ground to the cold start injector. This ONLY is operational while the starter is operationing and it ONLY functions for so many seconds then shuts off (this is to keep from flooding the engine).

You may have a problem with the thermoswitch or the cold start valve.
If you have a wiring diagram or can determine which wire goes from the thermoswitch to the coldstart valve you could disconnect it from the switch and ground it by hand while someone else is cranking the car over if it starts now you know the switch is bad.

Oh well I'm done rambling. Surely someone else with more experience will chime in and give you a clearer idea on diagnosing this problem.

[mperkins]

Simon, I had the same cold start issues for 2 years - and it was quite aggravating. I had it addressed by my mechanic and he did the following:

reconnected connection to thermo time switch, and reconnected fuel pump shut-off switch. Then adjusted my air/fuel mixture to 2% (i was running rich at 4%+)

Since then, my engine starts right up on the first turn - even after the car has sat for over 2 weeks.

It ended up having NOTHING to do with my fuel pump check valve, WUR, or fuel accumulator.

If you do a search here at Pelican under my name - you'll see a summary of the cold start problem I faced.

I hope this helps and you resolve it quickly!!

[stormcrow]

Simon,

There could be several issues related to your problem. To correctly troubleshoot you need to have a pressure gauge. However, you could do the following test to see if you are getting flow from the fuel distributor.

It could be your sensor plate is just a little bit too low and does not allow fuel to flow when you do a cold start. If you are fimilar with adjusting the sensor plate height, then turn the 3mm screw a quarter turn clockwise before you start the engine cold. Make sure you note how much you turned it because if this doesn't solve the problem you need to turn it back to its original position.

If the problem still persists, then I would invest in the fuel pressure gauge to further troubleshoot the problem.

Steve

"A Porsche does more then just go fast in a straight line"

[smestas]

Thanks for all the great feedback!

Today I managed to unplug the wires to the air sensor plate to get the fuel pump to stay on right when the ignition is in the ON position. Sure enough the car fired right up the first try. I’m not to sure what this proves other then my car is not getting fuel at start up. I think all of you are right when you say it is probably CSV or thermotime switch related. Ill try to check those next and keep you all posted. Pelican member "vash" was kind enough to PM me a some notes on how to test these two items.

Ill keep you all posted.

[smestas]

I forgot to mention that before pulling the sensor plate wires I tried to crank the car over (cold) with with one of the injectors in a glass jar and I got no fuel. So does this mean that when cold the car only fires up from fuel delivered by the CSV or should I be getting fuel from the injector and the CSV is only for enrichment?

[Gunter]

Simon: Sensor plate wires? Please, explain. You are right that the engine gets fuel from both the injectors and the CSV. You can test your pump for volume by disconnecting the fuel line from the accumulator. Connect a length of hose to disconnected fuel line. Place open end of fuel line in a container. (Min 2 quarts) Run fuel pump by jumping terminal 30 to 87a of the fuel pump relay (Ignition ON) for exactly 30 seconds. You should get a minimum of one liter, about a quart. Bentley 201-6. Keep a fire extinguisher close by. When was the last time you run a Fuel System Cleaner thru?

[smestas]

Originally posted by Gunter
Simon: Sensor plate wires? Please, explain.

On the back of the air sensor plate housing there is a two wire connector. This connection turns the fuel pump on and off as a saftey feature. If you get in your car and turn the key to the on position and hear the fuel pump whining chances are that the air sensor plate is dissconected.

I think my problem is a leaking fuel accumulator but I am still testing. At least I can run the way its set up but its not very safe since the fuel pump is running if the motor is on or off.

[smestas]

Originally posted by Gunter
Simon: Sensor plate wires? Please, explain.

Taken form another posting.

Originally posted by Jim Sims
If the wiring is in the original OEM configuration and the air flow sensor is working and connected the fuel pump in your car should only function when the engine is running (pulling air through the induction system) when the ignition key is in the on or run position. The fuel pump also runs while the starter is cranking. If it behaves differently than the above then it has been modified (usually the connector to the air flow switch is disconnected) or has a malfunction. If you want to check to see if your system is functioning correctly, the turn the key to on but don't start the engine. Then pull off the air cleaner cover and filter and reach up inside the air box and lift up the air metering plate. You should hear the fuel pump come on and feel the system "stiffen" as it pressurizes. Do not hold the plate up more than 3 seconds or so to avoid filling the cylinders with gasoline. Cheers, Jim

[smestas]

Gunter,

Here is a pic of where the connector is.