Fuel pump runs constantly

patkeefe · 08-28-2006, 04:16 PM

Well, I just finished putting the 78 SC engine back together after a full rebuild and addition of a BAE turbo. Got everything hooked up, turned the key to on...
The fuel pump runs. It's not supposed to. Looking at my Bentley book, it gives lots of ways to see why it doesn't run. I'm looking at terminal 50 being the culprit.
When 50 goes into start, doesn't it switch the action of the relay from hot in start to hot in run. I'm having a bit of trouble figuring why it's hot in run without engaging the starter, unless the relay is shorted.

I'll think about it over dinner, then try some more tests. I am open to opinions and suggestions.

TIA
Pat

john walker's workshop · 07:11 AM

the green plug to the sensor plate switch, when unplugged, will cause the pump to run with the key on. it grounds fuel pump relay terminal 86 when connected with engine not running. sensor plate lifts from air flow, contact breaks it's ground, and pump runs. it stock form anyway. maybe the wiring got adjusted with the turbo installation. brown wire, white trace. (EDIT, brown wire BLACK trace).

ruf-porsche · ruf-porsche's Garage

Did you start the engine? My fuel pump run the very moment I turn the key in ignition switch, and it doesn't stop running. My engine always starts, hot or cold, even if it been sitting for a couple of months. I 've been told that this is not suppose to be but as my father once told me, "If it ain't broke don't FUCH with it".

patkeefe · 08-28-2006, 04:51 PM

JW-I'll check the sensor plate wiring. It stands to reason something is screwed up back there, since I just had it all apart.

ruf-the good thing about a brand new not turned over yet engine is that you can see how much fuel gets dumped back out the exhaust ports when the pump runs for 30. I thought maybe it had to fill the lines, but how would the system know the lines are full?

I'm trying to get the static timing done, so I can't really leave the ignition on and dump 2 gallons of fuel into my engine

Thanks!
Pat

john walker's workshop · 08-28-2006, 05:17 PM

shouldn't be dumping fuel at all. something's stuck, like the fuel distributor piston, or maybe the mixture adjustment screw is cranked in way too far.

patkeefe · 08-28-2006, 05:26 PM

Another twist...I went to the garage and turned the key to start for the heck of it. Starter did squat, as in not turn over a bit, didn't even pull the solenoid, but it did slow the fuel pump down a bit. I did remove the relay and that stopped the pump from running, and I did check the sensor plate to make sure it wasn't stuck in the open position.
I have a lot of stuff packed into that engine compartment now. I'll read the wiring diagrams some more.

JW, although I had the engine apart, I left the CIS intact on the bench. The mixture screw is where it was last when running. I have my gauges on it, and it has 70 PSI when the pump is running, and is holding the pressure within the limits.

Pat

csstrask · 08-28-2006, 05:33 PM

Pat,
You may want to make sure that you have not filled the cylinders with fuel. If so your engine will try to turn, but it will be hydralically locked. I had this happen and had to pull the spark plugs and crank it to get the fuel out. Be careful if you do this, the excess fuel will come out with a vengance... May be better to pull it out with a bulb or something.
Chris

ruf-porsche · ruf-porsche's Garage

csstrask

77 Euro Carrera 3.0
67 Lotus Europa vintage race car
76 MGB
60 Bugeye waiting in the wings
assorted toyotas and fords

WOW another Lotus Europa owner on this forum

WHooo Hoooo

csstrask · 08-28-2006, 05:46 PM

RUF,
Here is a link to a couple of pics of my car. http://lotus-europa.com/460269.html
Chris

ruf-porsche · ruf-porsche's Garage

Nice Series 1 with a Gordini 807 engine in it.

I have a Gordini 807 engine for my series 2 with the dual weber carb setup, but haven't install it yet. I'm running a single sidedraft weber on the original 821 engine.

Now my 52 has the twincam engine with the dual weber setup.

oneblueyedog · oneblueyedog's Garage

The fuel pump relay could be a part of the problem. For the heck of it try switching it out to see if it stops running off.

patkeefe · 08-28-2006, 06:08 PM

Thanks. Tomorrow is another day. I'll let the fuel evaporate overnight. And, I'll try to pick up a spare relay. I'm sure I screwed something up in the wiring.
Pat

patkeefe · 08-29-2006, 05:52 AM

Bump for the workday crowd. I'm starting to think I have the terminals incorrectly connected on the starter,and the CSV and airflow sensor plugs interchanged. I'll investige more after work.

Bentley doesn't even show the CSV on the main wiring diagrams.

mb911 · mb911's Garage

there is also a brown wire with a black tracer on the left hand side of the engine bay that tells the fuel pump relay that the engine is not cranking so it shuts down the pump. I think this is ultimatly what connects to the air flow switch but it has been a while since I converted to EFI

patkeefe · 08-29-2006, 01:54 PM

Ok, back to the garage with my trusty voltmeter...

Hoffmanmotors · 08-29-2006, 01:59 PM

Im having this very problem also, my pump always runs and was burning up relays. I looked at my fuel pump relay harness and found the wires melted together. got a short somewhere, so im off to sort it out.

Also, do you or anyone have a link to someone who sells the BAE turbo kit for 911sc? I cant find anything.

patkeefe · 08-29-2006, 04:05 PM

The good news and bad news. Wait, there is no good news.
I found that the wires from 15a and 50 were backwards, so the starter does indeed work now. That qualifies as somewhat good news.

The bad news. I disconnected both the cold start valve and the air flow sensor, and the pump still ran. I checked for continuity. I have continuity from both terminals of the air flow switch to ground. I ran a long jumper from 85 in the relay socket to the engine compartment, and I have continuity again at both terminals. I have deduced there is a dead short in this connection to the air flow switch. I wrang out the CSV wiring to the TT switch, and that's ok.

Running pump at 70 PSI for a short period produces fuel coming out of the exhaust (the 10 quarts of new oil are probably contaminated also). As JW said, the control plunger is stuck. I tried to backflush it with compressed air and carb cleaner, but that was a useless endeavor. So, now my options are remove the engine to make life easier, or remove only the fuel distributor, again to make life easier. Either way, I have to take the fuel distributor apart and see what's up. I may need a new one ($$$$), or maybe I can fix this. Do I have anything to lose here? And, I still need to rewire some of the stuff back there anyway.

Bummer.
Pat

iamchappy · iamchappy's Garage

Pat I wish I could help more but it all seems covered. Ive never had tis problem so my suggestions are just stabs in the dark, good luck,if i can get mine all together my whole SC CIS intake would become available.

Pull those injectors and stuff them into the six pack of empty beer bottles you have laying around now. it will keep the gas out of the engine untill they work as they should.

john walker's workshop · 08-29-2006, 06:18 PM

all you need to do is CAREFULLY free up the piston. there's a tit on the end that you may be able to grab with mini visegrips and gently work it out. do not score it or drop it! spray some penetrant into the top center port while you work it. probably just some gummy evaporated fuel holding it. needlenose visegrips, ground to fit may get it if the piston is too far in.
as for the pump running, ground the 86 terminal on the FP relay to test. that should keep it from functioning. brown/black wire from relay to 14 pin connector in engine area, to sensor plate connector. maybe the wires don't match up in the 14 pin connector. all it has to do is ground through the sensor plate contact when the engine isn't running.

ruf-porsche · ruf-porsche's Garage

Quote:

Originally posted by patkeefe
So, now my options are remove the engine to make life easier, or remove only the fuel distributor, again to make life easier. Either way, I have to take the fuel distributor apart and see what's up. I may need a new one ($$$$), or maybe I can fix this. Do I have anything to lose here? And, I still need to rewire some of the stuff back there anyway.

Bummer.
Pat

Whatever you do, don't take apart the FD. Once apart it will always leak. Someone did that last week on this board and he is looking to buy another FD.