fuel filters in the fuel system

[smokin_944]

How many fuel filters are there in the fuel system chain on Series 1 944s? I thought there were 2 but I could be mistaken. I am having a hesitation problem in acceleration that feels like a fuel feed problem possibly due to crap in the line. I have changed the silver canister that was filthywith a new one but I still get a hesitation in acceleration for a moment before it clears up. I have run injector cleaner and I use high octane gas (93). Ideas anyone?

[944 Ecology]

There is a strainer (I think of it as a large rock/small kid strainer) but that should not cause a fuel feed problem

Check the fuel pressure and the fuel delivery rate as described in the factory workshop manual.

[smokin_944]

Thanks George, I will do that...

[curtisr]

You bet a clogged fuel tank strainer can result in fuel issues.

[Monkey Wrench]

check with others as I havent had 944 injectors apart but the ones I have had apart ( volvo and ford of the 88 or so era) have a screen in the inlet of each injector. its a little basket and there may be a removal tool which is basically a puller with a sheet metal screw.

I ordered some and made a rig to test and observe the spray patterns under pressure, what I do is backflush them first.
if the screens are not plugged and backflushing proves no resistance, then I'd leave them be. but change the orings and theplastic washers and the pintle.

the only strainers like the one in the pic i have seen are close to 100 bucks so I might make my own with somegasoline screen and a brass fitting, or similar, save a hundred bucks or so. I can get a strainer for a volvo in tank pump very cheaply online

I just had a volvo filter plug up, it is a similar cannister filter. I remved it and could not blow through it so it needed to be replaced. that proved it was a problem.

if you are in there I'd replace the pump if not done.

be careful I think yours has a metal tank and mine is the same, the hose that comes out of the tank to the filter , on mine rotted and let go of ALL its fuel, this is a very dangerous situation so change that hose. you do not want a tank of gas to unexpectedly leak.

you can go changing the flexible high pressure lines some reported engine fires there is a video showing to cut the lines and use a type of comression fitting.

you might save by using aluminum fittings rather than OEM. after the pumo it is a high(er) pressure system , before the pump it is just gravity fed from the tank.

they tend to be proprietary parts otherwise and I havent found economic sources. if your budget allows you can get porsche parts and keep it OEM. that is nicer.

metric line and crimprers for it may not be common in your area so a switch to a more universal type of fitting might save a bit. fuel system parts commonly used on boats and race cars are likely just fine but a lot of the aluminum fittings are powder coated in bright ugly colors and stand out as non OEM.
you can get thick hose that is marine rated, maybe a bit more safe than any other fuel hose. probably wont kink easily. youcna get hose rated for fuel injection systems.

after my tank leaked it sat there and oozed stuff like shown in the pic,,

Ill use a used "in tank fuel pump" wiht its strainer , drop it in a bucket of solvent and wash out the tank well with recirculating fluid, solvents or what you wish. I plan to hose mine out and if you want o you can remove the fule guage assembly and wipe it from there, maybe tie a rag to some flexible wire and wipe best you can in there , with some solvent or similar.

the metal tanks were reported to have issues with being stretched during manufacturer causing rust or maybe stress cracks near where they were work hardened. on top of the tank.

you can recoat a gas tank with a por 15 gas tank repair kit but be aware that tank removal requires transaxle removal, it may be good to do that if you are doing the clutch drive tube bearings CV joints etc to avoid removal of transaxle twice. if the car stinks of gasoline it may be a rupture in the top of the tank.

mine has the rubber centered clutch so yours likely is , evidently the rubber degrades and it may show up as rubber dust anear the starter area, when the rubber degrades the cluch doesn't slip but it develops a clunk because it has no springs.. rubber just has a life expectancy and it is unfortunately shorter than the car is old.

The clutch is also very expensive OEM .. If there is a compatible clutch with more normal springs and you find info on something compatible , let us know , Personally I am not really looking forward to dropping a thousand bucks on only a clutch kit but it may be an inevitable cost.
you can get cheap offshore fuel pumps, I'd stick wiht the bosche one, and there may be more than one grade of bosche pump. I'd spend the 200 or so and get a good one.

the pump does not make pressure it makes flow, resistance to flow creates pressure, the fuel regulator does that , it provides resistance, and unused fuel is returned to tank. you can check fuel pressure on the fuel rail to be siure the regulator is working and the regulator has a line to vacuum. as the throttle opens the vacuum is reduced ( air gets into the manifild more easily with a open throttle plate) reduced vacuum means more fuel is needed so the regulator boosts the fuel pressure a bit..

the "barn door flapper thing" and electronics relate RPM and throttle open to give the DME (AKA ECU in other cars ) . the input it needs. this in turn changes the very short momentary open time of the injectors. the injectors pulse in pairs and not in the firing order as you may at first expect.



i fthe refgulator has a ruptured diapram you may see or smell gas in the sensing line.

there is also a fuel dampener on the fuel rail. it basically takes vibration shocks and noise out to of the fuel sustem, comparable to water hammer in plumbing but higher frequency.

clark's garage has helpful info if you cant; find that site ask, it will help lots.

you can clean the sliding contacts in the "barn door", you can chek for leakdown on the fuel rail. if the contacts are dirty it may give eratinc info and affect smooth accelleration.

if an injector sticks open the fuel rail pressure can't maintain .. there is also a check valve near the pump and if it is leaking it may also allow flowback and that looks like leakdown to a fuel pressur guage.. similar symptom .

if an injector sticks open it can pour raw gas into its cyinder and you may see white smoke on startup. until the raw fuel clears.
maintaing fuel pressure on the rail helps it start easily and quickly.

vacuum leaks will upset the idle so check for leaks you can do a "smoke test" to look for leaks , Id check any hoses connected to the manifold and the PCV system PCV fumes are "dirty oily air" so it may rot out hoses.

i fyou pull the fuel rail out you can connect the grounds and see them spray , thi sis never a recommended procedure in any manual Ive =found, because you can spray gas around and cause a big explosion. think it through if you do "foolish" stuff like that. I do not want my suggestion to cause a fire or an explosion. i do find it helpful in analizing but it is or could be dangerous and not a recommended troubleshooting process due to the assoiciated dangers. please dont take them lightly.


I made a bottle which I fill partially with cleaner connect a hose to an injector it has a tap on the bottom of the bottle before the injector. use about a 1/2 " hose and a clamp.

I pressurize the bottle to a=round 50 PSI. I open the tap , pressurizing the injector, I provide 9 volts from a battery, it opens the injector so I can see the spray, I like to pu thtem backwards foirst and backflush then check them for a fairly normal spray pattern.
I do this outdoors with a fire extinguiser ready , you can probably flush with non flamable brake parts cleaner. be caureful because atomized gas or some cleaners are not only extremely flamable but also explosive

if I can check an injector and see a fairly normal spray then the reason for the car not starting is probably not because of the injectors. and it is not fule starvation. If you like you cna replace with rebuilt or new or offshore ones.

if you monitor fuel pressure at wide open throttle and then see fule pressure fall because of high fuel demand that may be a sign of a plugged filter, tank screen etc,, if it maintains pressure then it is unlikely to be a fuel starvation problem.

to connect a guage and monitor it is a little awkward and you may need some fuel line fittings to connect it , and and a long hose or some sort of plan to see it , cell phone video maybe? got access to a dyno ? I bought a cheap endoscope on amazon it has a long cable.. may work to view things like a FP gauge from some distance or under a closed hood. .