Fuel Accumulator Symptoms?

[mooney265]

After reading and reading through numerous posts on start-up problems, I'm pretty convinced that I have a bad fuel accumulator.

Basically, the engine starts up when cold [it takes about 3-seconds to fire]. Once it fires, it takes about 10-15 seconds to get running smoothly [it seems like it's starving for fuel - - running a little lean]. Eventually, it begins to run smooth and continues to run smooth thereafter...

Once warmed up, if I kill the engine, I can restart it [while still hot] very easily. It immediately starts running like it was before the shut down...

However, if I kill the engine and let it sit for say 30-45 minutes, and try to restart while still a little warm - - i can just about forget it! It takes about 10-15 seconds of cranking and when it finally fires, it takes about 10 seconds to go from 100 rpm to 900 rpm while it continously struggles for fuel... For those 10 seconds, it doesn't even seem like the engine is running...

Q: If not the accumulator, then what?

[mooney265]

BTW: How hard is it to access and change the accumulator?

[A930Rocket]

Easy to do. You'll need to remove the intercooler (and possibly the fuel filter to make it easier). Do it with a cold engine and use rags to catch the gas when you loosen the fittings. It will probably take two hours.

BTW: How hard is it to access and change the accumulator?

[infraredcalvin]

When hot, then off for about an hour, mine does the same, does not fire on all six, then settles down. I've had all the wur changed, fuel pumps replaced, fuel acumulator replaced... my mech believes its the fuel distributor (not holding the pressure and allowing gas to vaporize - this is typically the function of the accumulator when all is functioning well). The fuel distributor is a nut I don't want to swallow yet...

[AFM744]

I had been blaming my accumulator due to similar symptoms, until last week when I had to pull my manifold. Lo and behold, in the #6 intake port there was about 1/4" of gas pooled on top of the valve; a leaking injector.
If you're going to chase down your hot-start issue, do yourself a favor and make sure your WUR (new, old, whatever) is providing proper control pressure for the temp. I just de-AAR'd and de-Vac-Reg'd my car and it still starts better than when my cold control pressure was off.
Also make sure you have no air leaks, that your injector block stud nuts are all torqued. An air leak will cause its own starting issues.

[lucittm]

Jon,
Did you remove both the aux air regulator and the vacuum limiter at the same time? I was wondering which one made the most difference to the throttle response and starting? What did you use for caps where the hoses were? Let's see a picture of your tidy engine under the intercooler...

Your cap should arrive there today or tomorrow. I sent it First Class.

Mark

[AFM744]

Mark-
I pulled both. I swear the back of the car rides higher with all the smog removed plus that other crap!
Yes I did two changes at a time. I'm too impatient to be methodical.
I capped the manifold spiggot that went to the VacLim. I capped the intercooler spiggot on the left side. The intercooler-to-AAR hose now goes to another Bosch 710N Bypass Valve. The vacuum hose that went to the VacLim now activates that BPV. Some other turbo guys and I were suspecting the single BPV on our car is not large enough to dump induction charge so I'm just experimenting. So far it drives better, but the second BPV vents to atmosphere so my car sounds like a stoobit SRT4 "waaaaaaah-kshshsh"

[jwasbury]

Originally Posted by AFM744

If you're going to chase down your hot-start issue, do yourself a favor and make sure your WUR (new, old, whatever) is providing proper control pressure for the temp.

Excellent advice here. Get yourself a set of CIS pressure test gauges from JC Whitney (pretty cheap). You can use these to check your control pressures maintained by the WUR, and also to see if your accumulator is properly holding the fuel pressure after shutdown. The accumulator is not cheap, so you'll be pissed if you replace it and it doesn't fix your problem.

[lucittm]

Jon,
I don't think the aux air regulator causes me any drama after the car has warmed up, so I will leave it for now. The vacuum limiter is a different story. I can't figure out why it really needs to be left in place. I will use the official Porsche cap (930-110-256-00) on the manifold and the intercooler just for fun.

I be you are a big hit when you cruise Stoneridge Mall in your car and it goes wah hah-cushshshsh.

I'll let you know what difference I can feel, if any.

Mark

[AFM744]

"...cruise Stoneridge Mall..." I resent that! I hate the mall and I certainly try to take the Montero, not the Porsche if I'm forced into it.
As for driving impression; the VacLim-ectomy definitely gives a bit more off-throttle engine braking. The 964 cams took some of that away and until the rings broke in this engine had no lift-throttle braking to speak of. Now I have some engine braking again, and when I blip the throttle the engine comes RIGHT back down instead of hanging and lolligagging. It's not a LWFW, but it's definitely better.
EDIT: I yanked the AAR as well simply to continue with the de-clutter. You know how nice it is to be able to reach the WUR and the idle adjuster by hand? Hell, last night I spilled oil. You know how nice it is to WIPE DOWN YOUR SIDE TINS?!?!? I never SAW the damn things before!!!

[mooney265]

Just got back in... Thanks for all the posts!!

I didn't realize it was located under the intercooler... Had it off the other day and didn't notice.

I guess I'll need to purchase a CIS test kit from the host or JC. that should tell me if i'm getting the correct pressure from the WUR or if the system is holding pressure as time clicks away...

I'm not ready to remove the AAR, etc... I just tackled the Air Box last weekend. Got Brian's 6 3/8" round air filter now.

It sure is nice to see all those things - - before I remove them!

[Miguel Antonett]

Did the problem begin after the new air filter installation? If so, check the mix telescopy adjustment bolt - it should be touching the filter (but moving freely via notch on the filter rim) on the driver side, and fully extended - sometimes it stays down, it should pup up (by a spring); worst scenario, it is disconnected/broken at the base while installing the filter element. Ask me how I know...

[mooney265]

Miguel,

The mix adjustment bolt seems to be operating and intact. The new air filter does slightly rub against it...

It is in the upright position.

Now, I don't think it's supposed to be able to move freely on it's own, right? If it is, then there's definitely a problem... But if it can remain in the fixed upright position, then it's fine...

So, what happened to yours?

[x98boardwell]

Mooney265,

Did you ever figure out this problem? I have a new fuel dist. on my 87-930 and recently had the motor out for a top-end rebuild and it has never ran better... except within the last week I have been dealing with that same "warm start" issue that you were referring to.

I also have a digital AFR gage in the car and when I start the car warm it is extremely lean until I rev it up (takes some patience and 30 seconds) and then she calms right down to idle and normal AFR's.

Did you ever figure out your problem? Was it the fuel accumulator? I'm hoping that I don't have to send this fuel distributor back. Did you do the WUR pressure testing?

I think we are/were dealing with the same thing and could use your outcome as help. I will also send you a PM. Hopefully you are back up and running good.

Thanks,
Bryan

[9dreizig]

Bryan, I"ve got a CIS fuel pressure set if you need to borrow it.
Todd

[x98boardwell]

I may actually take you up on that. When will you be touching base in Fresno again? If not, we can figure out how to meet up.

Let me dig a little further first but I appreciate your help. I have one from HF but am afraid that it will give me false readings since I had such a disaster when I used HF's Leak-down test kit... it didn't work at all.

Thanks again and I will be in touch,
Bryan

[turbobrat930]

I have a Almost brand new fuel accumulator that I dont need anymore...if it turns out that yours is the problem....

[mooney265]

Originally Posted by x98boardwell

Mooney265,

Did you ever figure out this problem? I have a new fuel dist. on my 87-930 and recently had the motor out for a top-end rebuild and it has never ran better... except within the last week I have been dealing with that same "warm start" issue that you were referring to.

I also have a digital AFR gage in the car and when I start the car warm it is extremely lean until I rev it up (takes some patience and 30 seconds) and then she calms right down to idle and normal AFR's.

Did you ever figure out your problem? Was it the fuel accumulator? I'm hoping that I don't have to send this fuel distributor back. Did you do the WUR pressure testing?

I think we are/were dealing with the same thing and could use your outcome as help. I will also send you a PM. Hopefully you are back up and running good.

Thanks,
Bryan

Bryan,

Yes, fuel accumulator... The problem was very intermitent, though... I believe there was a "sticky valve" of some sort on the accumulator. so, sometimes it would do the job and have no problems, and sometimes [25%] of the time it would release the fuel pressure...

Make sure you check the pressures multiple times with the equipment hooked up...

that's my best guess...

[A930Rocket]

Depending on ambient temps, you may need to richen it up just a hair to help it get started. I know when I've gotten my car dynoed, it runs like a champ, but when I'm at the track on a cold day, I end up richening it the AM to get it started. Just a thought.

[356-930]

Hot start issues on 930 CIS motors can be caused by heat soak vapor lock, bad accumulator or high control pressure (lean). Can’t imagine the fuel head having anything to do with the problem.
Unless you have added a bunch of stuff under the hood that would retain and radiate heat onto the WUR, probably not vapor lock. If the WUR continues to lean with heat, and it will get even hotter when a warm/hot engine is shut off due to heat soak, then control pressure can be the problem. And like some posters noted, it can readily be a bad accumulator.
All hot start issues I had with my engine, and they have been numerous, were the result of high CP’s with increase temp. When warm/hot CP is within spec, no hot start issue.
If CP is within range, (be sure to check it with a truly warmed up and heat soaked engine – be careful if disconnecting/reconnecting gages in fuel system on a hot engine, fire hazard) it’s most probably an accumulator issue.
My work around was to add a starter button activated ground wire to the ground lug of the thermal time switch (easy to get to). From its ground lug, run a wire to a starter button mounted under the dash. Ground the 2nd terminal of the button. When cranking, +12V is applied via the thermal time switch to the 7th injector and by pressing the starter button, the circuit is completed, turning the injector on. Pressing the starter button when driving does nothing as +12v is not applied to the thermal time switch. Yes, it’s a Band-Aid but it’s a reliable one.
A less reliable work around is to add just a little throttle when starting hot. Key is, just a little. I believe the cranking speed of the engine is just sufficient enough that with the throttle slightly depressed, the the sensor plate of the CIS moves enough to trigger the fuel head piston to move which adds enough fuel the engine and it catches. Adding a lot of throttle to an engine with a hot start issue does nothing to help it start.