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Check you fuel pressure regulators!

MarkGolf

PCGB Member
Member
I never did, had seen and heard of horror stories, experienced a scare and lived to tell the tale!

As our 964's get older, more will go wrong, it is all part of owning an old car. One part of the car, which I neglected due to being hidden away, was the fuel pressure regulator (FPR). This is what controls the fuel pressure based on your throttle input, in the way of a vacuum pulling a diaphragm inside the FPR. As the years tick on, this diaphragm gets weak, being pulled on, hot and cold cycles etc, it becomes weak and fuel gets through and sucked up the vacuum line and into the intake manifold where the risk of fire is at it's peak, for those unlucky enough, the fire gets to a point where it can't be put out, to others, they may get off lightly with just some charring and to many, it's an unknown, odd hard starting issues and minor fluctuations in idle speeds are put down to issues with MAF, vacuum leaks, old age, bad fuel.

In my case, I had warning signs but I was looking for resolution elsewhere. I had the odd hot start issue, where the car would crank for a while before firing up, it developed a misfire which had me change most of my ignition system and it also had a slightly lumpy idle which was the final straw before I had a fire.


I was lucky, I caught my fire before it got too big, I had damage to 2 of the rubber joiners between the throttle body and inlet manifold and the caps on my injectors were slightly melted. That is everything I have seen at this time, I hope that there is nothing else waiting for me.

So, if you don't know the history of your FPR, if it's original, just change it! Don't leave it until you get signs of a failure.

A quick test, is to pull the vacuum line which runs down to it, off, either at the FPR end (difficult to access) or the end which joins the 3 way rubber joiner at the top of the intake manifold (easy to access), if fuel comes out, you're in trouble but lucky. Other tests consist of hooking up a fuel pressure gauge to test pressure when cold, hot and running.

You can buy an original part from Porsche but it will cost you anything from £450 (RRP).
Original Porsche part number = 928 110 198 25

Or, you can go the aftermarket route, I did a quick bit of research and found 3 US based companies who make a billet housing which feature a standard FPR which is fitted to many modern day cars, so very cheap and easy to change, this route also allows you to upgrade without great cost. There are option to go with standard pressure or upgrade to allow greater fuel pressure if you are intending on performing some power upgrades to your 964.

I went with the option from 928sRUS. Purely because it was black in finish, so would remain fairly unseen, the other options were a raw silver finish.

https://928srus.com/products/928-110-198-25am-billet-fuel-pressure-regulator-88-to-95

I paid £209 including delivery from Texas and it came 6 days later. It came securely packed and with some instructions. Great product and service, so credit to 928sRUS. Run by a UK chap too.

I am in the middle of putting my car back together, so will update my progress diary as and when but the point of this post was just to alert you to a possible hazard on your 964's.

It took me no more than 1 hour to remove my intake manifold, which gave me access to the FPR, I believe some people did not remove the intake manifold to do the swap but I can't imagine how they got enough leverage on the spanners to undo fuel pipes to free the FPR from them. I wouldn't say it was a difficult job by any means, nothing complicated, just a matter of undoing jubilee clips, sensor plugs and disconnecting fuel lines. So if you are not confident in doing the job yourself, a garage shouldn't charge for more than half a days rate to perform the sole swap of the FPR. You could go some steps further, change fuel lines, clean the MAF and intake system internals, replace breather/vac pipes, refresh fuel injectors, I am doing these, purely for preventative maintenance but not always required.

It goes without saying, take precautions when dealing with the fuel system, keep a fire extinguisher handy, disconnect the battery, have rags and containers on hand, beware of a pressurised system.

I had seen a lot of talk online, in regard to aircooled Porsche fires and I was lucky to got away with not having one, like I did. So get your system checked or changed.

Part 17 is the fpr
51404182874_a3e93125ba_c.jpg


Cheers
Mark

 
Mark, Ive just commented on your rennlist to this ...I have a fuel kit in hand with a new fuel regultor, as you say there not cheap

Drop me line when you at the next Surrey meeting and i'll bring my Bosch Hammer along for your reset
 
Nice one Ian, just replied to you over there.

The FPR was the cause of my issues, clearly. Love the look of those fuel lines.
 
Hmm.. prudent to check mine too I guess. No running problems so far. You think it would also improve throttle response (either the std or higher press FPR)? Wonder, as 2nd gear changes, from 3rd, the throttle blip is non-existent - down through higher gears all good.
 
Slightly odd, would have thought your blips would be the same regardless of gear.. I doubt it's related but a failing fpr could result in weak pressure but probably more so under load.

After seeing my injector report, i'd say having those cleaned would make a difference but no necessarily the cause of your downshift blips being weaker in lower gears..
 
Thought I replied..

Aye, 3rd to 2nd gear blips are weak and may be down to the instant high-rev fuel demands not being met immediately (higher, as compared to going from 4th to 3rd say). Who knows maybe a new FPR will help.

Had thought about doing the recommended battery disconnect/reconnect followed by a spirited drive for any ECU mapping ROM reset. But tbh I sometimes wonder if all that talk and recommendation to do this is just a fallacy.
 

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