fuel question

[john 928]

car runs smooth when cold and can get rpms to 3500 rpm. as the car warms up it starts to hesitate and have no power. when it get to operating temp it starts running rough then stalls almost like shes starving for gas. i pour some gas down the throttle and it runs perfect then stalls. if i just start the car and let it run it runs for a few minutes then drops idle and stalls. just before it stalls the fuel pump in the rear stops making that buzzing noise then right after that she stalls.

this is what i have done so far
timing belt , crank seal, idle pulley, new battery, slave cylinder.
i put 10 gal of fresh gas and added some fuel cleaner in the gas.
im thinking the fuel additive is causing my problem. my next step is to replace all the fuel lines and filter.but without any manuals im not going to attemp to take apart the fuel dist.

has anyone had this problem before.

[kelanel]

cleaning both the fuel distributer and warmup regulator will be vital at this point, WUR sounds like the culprit in this case

[MPDano]

Originally Posted by kelanel

cleaning both the fuel distributer and warmup regulator will be vital at this point, WUR sounds like the culprit in this case

I agree. Have you cleaned or removed the tiny screen in the WUR Inlet? Especially since it's temp related. Plus, it runs fine when bypassing the WUR and dropping gas right down the throat. Also, won't hurt to clean or remove the tiny screens in the distributor as well.

[Danglerb]

Originally Posted by john 928

just before it stalls the fuel pump in the rear stops making that buzzing noise then right after that she stalls.

Fuel pump relay, fuse, wiring.

[john 928]

I checked fuses and relays and those are fine but I think I'm losing fuel pressure or power at the pump. But I am going to clean out those screens I still have to do the fuel lines , brake calipers and. Rear axle boots and hopefully I can get her on the road. That website sharkskin really helped me out. I did the entire tbelt and pulley tensoiner job with the help of roger from 928rus and skarkskin. I'm not a mechanic by trade but I worked as a parts guy for toyota for 20 years and I'm never afraid to tackle any job.
Thanks for the tip to clean out those screens , I. Was going to start with the fuel lines from the tank and work my way foward the eng

[AirtekHVAC]

Definitely do the fuel lines. You will be happy you did!

[lfausty]

do you know if you have more than one fpump some pcars can have up to 3, and locations , fpump/s in and/or under tank and a fpump can be pass rear fender well. as well a fuel accum in fender well.


def the warm up reg/ wur troubleshoot, orings gaskets to it? as critical as the f dist working great.
if theres idle control valve/icv sticky not clicking-decarb. shake/listen? test?

[john 928]

i know about the fuel pump in the rear tank and there is what looks like a accumulater and a filter or the other pump on the rt rear wheel. but i think thats all. i purchased the kit from roger 928rus to do all the fuel lines and didnt see any other pumps. i had the car running perfect after cleaning out the rear fuel pump but then the tbelt broke. from what the old owner told me the car sat in a big garage for about 10 years with three other porsches 2 928s and a 911 but the 911 was hurting and needed a full resto the other 928 was a 83 atm. everything on the car is dry. so i will eventually replace all the hoses on the eng

[Danglerb]

CI$ can be very reliable, until debris gets into the system, and then its seems everything gets replaced or rebuilt before its running well again. Last CI$ car we had I was tempted once it was fixed to plumb in a few extra fuel filters.

[lfausty]

did you see fuel inj? did they come out in one piece, curious. they must of been beyond varnish, seals/oring gone bad . and inj break off getting them out even?

[DPW928]

Incorrect valve timing can also cause the problems you are seeing. The extra fuel in the intake may be compensating for retarded timing on the intake valves. When you changed the timing belt, did you line up the notches on the back of the cam gears to the pointers? Have you rechecked the belt tension to make sure it isn't jumping teeth? Did you disturb any vacuum lines during the timing belt change? That could also be the culprit.

[john 928]

i set the crank on zero and lined up the two top gears ran the motor and checked after that and was on the mark. when i put gas in the throtlle when cold it would rev smooth all the way to 4000rpm smooth so iim thinking the timing is good.i checked all the vac lines and seem to be on but to get under there is tough. i took off the air cleaner to check. i just took off the wur and found grease on top of the spring cap where the pin sits in. or is that grease gas sludge. i found only one screen in there. do i have to take those 4 screws off on the inside of the wur to clean the screen??????????? i took some photos of the wur and the fuel pumps. can anyone tell me if the setup by the rt rr wheel is a filter or a pump. i was told its a accumulater.

[DPW928]

The "sludge" is probably a lacquer build up caused by old fuel. The 4 screws at the bottom of the WUR is the housing for the diaphram that leans the fuel when decelerating. You can check the diaphram by seeing if it will hold a vacuum. I would recheck the cam timing and tension. You also may want to recheck the ignition timing since a cam timing change can affect the ignition timing.

[john 928]

i just put eveything back and rechecked the timing and ign. if im correct the dist rotor should face down about 6 oclock and crank TDC and i lined up the marks right where they should be. it ran much better but im losing fuel pressure i think from the main pump in the back by the tank. its making a buzzing noise then all of a sudden i can here the pump slow down then the car starts to bogg down and wants to stall. while i was standing by the back of the pump the pump kicked back on then idled back up and started running ok. i think its the fuel pump not producing enough psi and bogging down the eng. how do i check the pump to see if its putting out enough psi.

the pump im talking about is in the last picture now remember i had to reverse the power in the pump when i first got the car to get the pump to work because it wasnt pumping.
im thinking a new pump is in order.

[AirtekHVAC]

John,

On my 78, there are (2) fuel pumps. One under the tank, and one to the left of the passenger rear wheel, near the filler neck, opposite of the accumulator assembly. The fuel goes through the filter, and then the accumulator IIRC...mine was shot. I am going to try to run the dual pumps and filter w/o the accumulator.

I suggest you replace that filter....

[DPW928]

Setting the ignition timing by sight is fine but it now needs timed with a timing light to make sure it correct. The output of the fuel pump is measured at the inlet connection of the fuel distributor. The output should be 1100 ml in 30 seconds minimum. The intermittent operation of the fuel pump is probably due to corrosion somewhere in the circuit. First place to check would be the ground connection when the negative wire from the pump attached to the chassis. Next, check the fuse and relay contacts. Check the connector on the green wire that runs from the ignition distributor. It is on the left side/front of the engine, near the fourteen pin connector. Check all the pins on the fourteen pin connector. The last place to check is the contacts of the plug to the ignition module which is mounted on the drivers side wheel well.

[john 928]

i will check the connections and fuses and relays. i just found that one of the leads on the dist cap had broke off in the wire. do you think that one wire would make it run like that.
im replacing the cap tomorrow

[DPW928]

The broken plug wire would make it miss but would not account for the stalling, etc.

[dcrasta]

I had a bad 53 fuel pump relay that would fail after it got hot. YOu can get 53 relays from the junkyard, look in VW Jetta's (under the hood).

[john 928]

when it starts up i have smooth accel to 3000 rpm and as it gets warm it drops to 2000 rpm after 2000 accelleration breaks up then boogs down.
im going to test voltage at the relay and pump and check fuses.

ill keep everyone posted if i fix it today