924 dies in traffic

james999 · 05-20-2008, 04:27 AM

Hi again

my 78 924 runs just fine on nice highway runs and in town when there isn't traffic. but as soon as i get stuck in stop start traffic then the car starts giving problems.

the fuel pump gradually starts whining more and more, and then when the traffic does clear up the engine rev's freely up to a point and then the engine runs roughly, as if it is being starved of fuel. if the traffic persists then the engine begins to stutter and eventually dies. following this people in fiat UNO's drive past laughing as i'm stuck pushing the car to the side. but back to the problem. the car does not start after that happens and i cant hear the injectors spraying when i lift the Air flow sensor manually. if the car is allowed to cool down for a while then it starts again perfectly and runs till i get stuck in traffic again.

any help would be greatly appreciated....

jmd_forest · 05-20-2008, 04:46 AM

Try changing your fuel filter. Cheap and easy and if it doesn't fix the problem, its one less variable to deal with.

jmd_forest

ideola · ideola's Garage

Quote:

Originally Posted by james999

the fuel pump gradually starts whining more and more

A clue. Perhaps time for a new fuel pump before it quits for good and really leaves you stranded. If you can source a 6-6.5 bar pump, you can also eliminate the in-tank pump which may also be dead. Here are some options for the Pierburg aftermarket replacement unit that will work for the 924, although I'm not sure if they ship to SA.
http://www.shokan.com/catalog/product_info.php?products_id=451
http://www.***********/acatalog/Pierburg_Fuel_Pump__911_77_80.html

924RACR · 05-20-2008, 05:38 AM

Like ideola said... also doesn't hurt to check and clean all wiring to and from the fuel pump including ground (in the hatch area, by the license plate).

Airflow while you're moving is probably fine to cool the pump, but fuel flow alone should be enough - so your pump is probably on the way out.

bud9344 · bud9344's Garage

For sure it is your fuel pump ready to go.
Happen to me on my Truck fuel pump winding as I was driving out off town up to the point,I turn around and head back home. It keep cutting out and baby the acc pedal to speed and stalling every traffic light. luckily I got back home drop it off to my Shop and replace the fuel pump.
------------------
Bud

John_AZ · 05-20-2008, 08:02 AM

Does the fuel pump relay get really hot especially by the top fuse holder?

[img]

When I owned a '77.5 and '79 924 this was a major problem in hot weather/city driving in Arizona-yesterday 110 degrees F in Phoenix. I replaced the relay more than once and put heavier battery cables and an additional ground setup to block. I cleaned all contacts and ground points.

Good Luck

John_AZ
1988 924S + 1987 924S = to show/to go
1977.5 924 + 1979 924 = gone/gone

james999 · 05-20-2008, 08:17 PM

I have installed a separate earth cable directly to the block and i have cleaned all the earth terminals and installed a new fuel filter.

I will confess that i am not using the fuel pump relay shown, because it is simply unavailable in south africa and when i got the car it was just hard wired to turn the pump on when ignition was turned on. though i did put two relays in series, the first opens when the airflow sensor is lifted, and the second opens when the ignition is turned on. but yes the one relay does get hot when the problem starts happening.

would trying to source the proper relay really help? because what i have installed now does basically the same thing?

could it be my fuel distributor by any chance?

John_AZ · 05-21-2008, 05:11 AM

Quote:

Originally Posted by james999

I have installed a separate earth cable directly to the block and i have cleaned all the earth terminals and installed a new fuel filter.

I will confess that i am not using the fuel pump relay shown, because it is simply unavailable in south africa and when i got the car it was just hard wired to turn the pump on when ignition was turned on. though i did put two relays in series, the first opens when the airflow sensor is lifted, and the second opens when the ignition is turned on. but yes the one relay does get hot when the problem starts happening.

would trying to source the proper relay really help? because what i have installed now does basically the same thing?

could it be my fuel distributor by any chance?

I don't know. The setup you describe may be the repair I should have used. My relay would get so hot the fuse terminals melted the black relay case where the prongs came through. I hope someone else has information for you. Good luck.

John_AZ

ideola · ideola's Garage

The experts on this are over at 924board.org. You should try posting this topic over there under the General Discussions forum, and provide a cross-link to this thread. Also, you may be interested to know that there are at least a couple 924 enthusiast on that board that are from SA.

Good luck.

924RACR · 05-21-2008, 06:29 AM

The wiring shouldn't get hot like that. The heat is because too much current is being drawn. This is either because your pump is dying or because something else in the wiring there is corroded - takes much more current to pull the power through the corrosion.

For comparison, on my '79 racecar I have no relay, just a separate switch on the dash that will directly supply power to the pump. The one and only time it got hot was when the integral bulb in the switch died and melted, killing the circuit (and therefore the motor). Replaced it with a switch with an LED in it, so it won't melt again.

So you need to trace that whole circuit and find and eliminate the corrosion.

JonA · 05-21-2008, 05:10 PM

On the original fuel pump relay the coil is wired so that the fuel pump is de-energized when the engine stops. This is critical if the engine stops because you have hit a tree and ruptured a fuel line. Make sure your 2 relay replacement rig has this feature.
As I recall the fuel pump relay was common to a bunch of VW's that all shared the Jetronic fuel injection. My relays all came from the junk yard, a whole bucket full for $5.00.

Jon

james999 · 08:18 PM

I will check up on that 924board, thank you. And i'll go check all my connections again, but i cleaned them up and made sure they were corrosion free after the respray job. but it's worth checking again i guess. maybe also replacing the leads to the pump. I try normally avoid hitting trees :-P what exactly does de-energizing the pump do? you mean it switches off? Because it does do that as soon as the engine stops because the air flow plate drops down and breaks the connection. or when the ignition is turned off.

Ps, South Africa stopped importing that relay 4 years ago, and a new 1 if it was available would cost in the region of $300 US. I looked in a few scrap yards, maybe i must look in a few more....

924RACR · 05-22-2008, 05:12 AM

The fuel shutoff feature varied across the years; early years had the plate switch as you have, later cars used RPM from the coil/tach circuit. Which means a more expensive relay, IC's to process the signal. With yours, I think it's just that the relay grounds through your switch.

None of this changes the fact that your fuel pump's dying.

nynor · 05-22-2008, 07:16 AM

Quote:

Originally Posted by james999

I will check up on that 924board, thank you. And i'll go check all my connections again, but i cleaned them up and made sure they were corrosion free after the respray job. but it's worth checking again i guess. maybe also replacing the leads to the pump. I try normally avoid hitting trees :-P what exactly does de-energizing the pump do? you mean it switches off? Because it does do that as soon as the engine stops because the air flow plate drops down and breaks the connection. or when the ignition is turned off.

Ps, South Africa stopped importing that relay 4 years ago, and a new 1 if it was available would cost in the region of $300 US. I looked in a few scrap yards, maybe i must look in a few more....

so order one here and have it SHIPPED.