What are the Symptoms of a Bad Fuel Accumulator (on a 328) ?

This is good (if you mean the coolant thermoswitch in the expansion tank), but you should really check to see if it is functioning properly. The 328 coolant thermoswitch logic is -- it should be closed when "cold" and "open" when warm. When it is closed, it runs the air injection system, and it also "tells" the injection ECU "I'm cold" so the injection ECU increases the (open-loop) FV duty cycle to add richness. As a test, unplug the coolant thermoswitch and add a jumper wire to connect the two wires in the harness (simulating a "closed" cold thermoswitch) -- see if that has any effect on the cold start-up behavior (of course, only do this as a brief test as you don't want the air injection system operating during warm-running).

Also goodness (confirms that the protection relay is properly supplying +12V power to run the injection system), but, as described above, the FV duty cycle when running cold should be different from when running warm so the next level would be to quantify the FV duty cycle when cold vs warm.

Nothing wrong with doing this, but it only supplies a short squirt of fuel during starter motor cranking to initiate engine light-off. If your bad cold running persists for many seconds (and the engine does light-off OK), these are signs that this system is working -- but nothing wrong with putting a voltmeter, or a test light, in parallel with the cold start injector coil winding to confirm/deny.

One thing that you haven't mentioned is the warm-up regulator (WUR). This (horrible ) gizmo is the analog (thermomechanical) "computer" that is supposed to lower the control pressure during cold-running so the airflow metering plate deflects more for the same airflow which adds richness for cold-running. Measuring the cold and warm fuel control pressures (and the fuel supply pressures) is they only way I'm aware of that you can test the WUR for proper operation (and then compare the results to the specs in the WSM).

Good Hunting! You said it correctly with "With fuel injection, I should not have to push on the pedal" -- something needs to be fixed.

 

if you have steel fuel injectors, my money's on them. they rust and drip fuel while off. mercedes went to brass injectors awhile ago because of this. they and ferrari were the last kjet cars on the planet. i saw this many a time on mbs and then last year on the first 512bbi i ever worked on. and it had 6k miles on it. not cheap to buy-'bout 40 usd ea, i think-but they will make a difference. good luck, chuck.

 

Possibly cold-start injector, more likely warm-up regulator.

Unfortunately the warm-up regulator is a fairly expensive item that is not always available new.

They can be bought rebuilt for quite a bit less than new.

Test fuel system pressures (main and control) to identify the problem. If the control pressure isn't significantly lower than the main supply pressure at startup the fuel/air mixture will be too lean to easily start.

Dirty fuel injectors that "squirt" instead of "spray" can be a problem but usually can be cleaned, although you need a special machine to do it.

 

Do a search here for vendors for the brass injectors. I bought some a month ago for $20 ea.

 

This thread was a massive help to me with an identical problem. However, I would like to help anyone who reads it. The “coolant thermoswitch in the expansion tank” is NOT located in the expansion tank. That is a good old temperature sender. The Thermoswitch or “thermo time switch” which controls the cold start injector is located in the bottom of the V to the right of the oil filter. Mine was not supplying a ground to the cold start injector and was defective. If the switch fails to conduct a ground to the cold start injector it will fail to spay fuel while the engine is cranking on the starter motor and a few seconds after start up. Maybe the sender in the expansion tank is connected to the circuit but as far as I can tell its not. If I am missing something please correct me. I would hate to make someone go through a wild Goose chase!

Thanks to everyone who writes about their F car experiences,
MS.

 

A faulty accumulator will give difficult starting when engine is warm. Your cold start problem does sound like a 'lack or fuel' problem and can be due to bad WUR which modifies the fuel pressure as the engine warms up. The best way to know is with a fuel pressure gauge, tapped into the fuel lines. Harbour Freight quality units are available for about $100, get extra copper crush washers for the banjo fittings.

 

Simply pull the small safety fuel return hose off the accumulator after the engine is shut off. If there is leakage out of the accumulator it needs replacement.

 

Doesn't the check valve in the fuel pump hold the back-pressure, and don't the fuel injectors keep the system pressurized?

Apart from a crack or leak, how would the fuel accumulator be at fault?

I do agree with Dave that if there is fuel in the return from the Acc to the tank, then the Acc is flat broken.

 

When my fuel accumulator (Mondial QV) went bad amount of gas would "squirt" out the return fitting whenever I started the car. Just that one squirt -- otherwise the car ran fine. I replace the accumulator (around $100 online) and no more squirts.

 

The check valve closes the system after shutoff, but, without the Accumulator, if the temperature of the fuel in the system dropped a few degrees (which it will as the engine bay cools), the volume of the fuel would shrink a little and all pressure would be lost (liquid fuel is relatively uncompressible). The Accumulator is a "soft" storage chamber that has a much lower pressure change for a given volume change -- this greatly reduces the overall change in pressure if the captured fuel itself changes volume a little due to temperature changes.

 

Where'bouts did you find a $100 accumulator? I've got a Mondi 3.2 that needs a new one but I can't find it for any less than $200...

 

If you need 113978 = http://www.autohausaz.com/search/product.aspx?sid=zxruuu45y2252p55lotflq55&partnumber=0438170004

or

if you need 125135 = http://www.autohausaz.com/search/product.aspx?sid=zxruuu45y2252p55lotflq55&partnumber=0438170042

 

You need your accumulator for cold starts. It maintains fuel pressure and some volume for the FI system before the fuel pump kicks in.Think of it as basically a can with a strong spring and diaphragm in it . the can fills with fuel , rubber diaphragmwith spring behind it pushes against fuel to maintain pressure after the car is shut off. If they go bad there is a small vacuum line on the back that directs leaking fuel into intake.