goldhunter_2

do the fuel pressure regulators on a 1984 porsche 944 go bad very often? is there any way to test them to see if they are bad?



got the car running but hard to start and hard to restart it lugs in lower rpm of each gear I am almost thinking the fuel pressure is bleeding back off then picks up once engine is revved higher or at least that what it feels like to me and wondering if these two fuel pressure regulators are bad but don't want to spend a extra $130 to replace them if I do not need to

River

Yes, they can. The fpr should be changed out every 60-65k. The dampener should be changed too if it never has.

goldhunter_2

where is the dampener located

JohnKoaWood

Typical sign of them being bad is fuel leaking from the vacuum port.. pull the vacuum line off and see if there is fuel present there...

hard start and low end lugging could be a multitude of issues beyone a bad / poorly performing FPR.. fuel filter, fuel pump, anti drainback valve all come to mind...

FPR has 1 fuel line connected to it, and a vacuum line, rear of the fuel rail.. dampner is front of the fuel rail, 2 fuel lines attached, and 1 vacuum line...

goldhunter_2

don't notice and fuel in those lines , so then no fuel would suggest the FPR's are still working properly?

car has new in-tank fuel screen, new fuel pump, new fuel filter.

where s the anti drainback valve located?

AKA_951

Connected directly to the fuel pump. Hopefully it was replaced along with your pump.

It may not be fuel pressure. Mount a gauge to be sure if you can.

JohnKoaWood

The valve is in the front of the pump, the banjo fitting attaches to it when the pump is installed...

No fuel in the vacuum lines doesnt mean the FPR or damper are good, just means the internal membranes are still intact..

you would need a fuel pressure gauge to test the FPR and drainback charachteristics..

Later this evening I can post the factory tollerances for these parameters.. I dont have my book with me at the moment!

86 951 Driver

If you can hook up a fuel pressure gauge to the rail you will find out within a minute of your car idling if your FPR is bad.

Depressurize the fuel lines. (Pull Fuel pump fuse start and run til it dies.)
Hook up a Fuel Pressure Gauge
Put fuse back in and start the car
Look at the gauge. Have the car idle for 30 seconds. If the fuel pressure is still good then give the car a quick rev and check again. If the fuel pressure spikes the gauges or goes higher than say 2.5 bar its bad.

I did this and found out really quick that my damn FPR was bad. I spiked the damn gauge. My fuel pump would get really loud to try and keep up with the demand.

gtroth

Hot start problem is a pretty good sign of bad fpr. Fuel pressure leaks down while sitting and since it's warm when you restart, dme gives it no enrichment. Any cause of fuel pressure leak down will do this (leaky injector, say).
Get your hands on a gauge and measure pressure and leak down.

dirtyTurbo

Mine was bad when I bought the turbo. Of course it was easy diagnosing with the vacuum leaks dripping fuel

So yes, it's not entirely uncommon. Sounds like a great excuse to go to the 3 bar

Grandpa#3

You Gents have overlooked the fact that the PO has a 1984 944. Check out the link below for the Fuel Pressure Regulator. It also shows the location of the FPR and Fuel Dampener on the 1984 model.

http://www.clarks-garage.com/shop-manual/fuel-07.htm

Cheers,
Larry

Raindrop

I saw some really cheap FPR for old model 944 cars on eBay lately. It might be worth it to just buy one to keep as back up : https://www.ebay.com/itm/113976658902 & https://www.ebay.com/itm/363095098380

88Silver924S

Hard start and lugging at low RPM sounds more like a vacuum leak somewhere?

Really old carburetor cars (think 1960's) had a fuel pump that ran off a lobe on the engine cam. Our electric pumps produce fuel pressure/delivery volume independent of engine RPM. So fuel starvation is evident mostly at high load or high engine speed on an electric fuel pump car. Correct me if I'm wrong.

I just realized this posting is from 2011. Was the problem ever solved? How do I delete this reply of mine?

DIYguy

Mind if I jump in here (new poster, very first post). We just purchased an '87 924S with the 2.5, pretty much the same set up as the 944. I've spent the past 2 weeks learning all about this car. Bottom line is I have a rich fuel situation and I'm looking for the best place to start? FPR, damper? something else?

The car runs rough and reeks of fuel but I see no leaks. The other night I let it idle for 10-15 min while I was checking vacuum lines and it eventually stalled. Came to take off the air filter cover and low and behold there was at least 2 cups of fuel sitting in there. It was not pure fuel, but 80% so. Was dirty and oily and slightly thicker than fuel. Other than the main butterfly valve for the throttle body, there are a few hoses that connect to the curved boot that could be what is supplying this fuel mixture.

I've since removed the curved boot that connects the air flow sensor to the throttle body and obviously the rubber lines underneath it. When I start the car (yes without the air filter or boot), after a minute or so I can see fuel coming from the hose that goes to the idle control valve. So my question is where is this fuel coming from? Isn't the IACV supposed to allow air from the curved boot to get into the intake, bypassing the throttle body butterfly valve? This would be in the opposite direction of this fuel that appears to be coming out of the hose from the intake side. What other connections does the IACV have? Is it electronically or vacuum controlled? I think its electronically controlled, so if no vacuum lines to allow fuel to leak into it, then is the only other inlet/outlet connected to the bottom of the intake and I probably have fuel coming backwards into my intake and going thru the IACV in the opposite direction?

So do I suspect high fuel pressure? Is my next task to check the pressure on the rail? Just looking for guidance and I'm still learning this fuel/emission system. The person we purchased this from said they replaced all the injectors. I did drive it home so maybe under more throttle the gas is forced thru the engine, but at idle it goes backwards. When I drove it it was sluggish and reeked of fuel though.

Jfrahm

Probably the FPR or damper is blown and leaking fuel through the vacuum port.