bryce.hanson

Hey guys this issue is a little hard to explain, so I made a video showing the issue I'm having. Does anyone have any insight?

bryce.hanson

Video didn't seem to work.

Here's the direct link: https://www.youtube.com/watch?v=MuqS...ature=youtu.be

bryce.hanson

Some specs for you guys:

1984 Porsche 928s
I believe it's L Jetronic
76k miles.
I've replaced the Fuel pressure regulators and fuel dampener. New fuel pump and filter.
I haven't replaced the Air Flow Meter, but I have replaced the Oring between the AFM and the throttlebody.

I'd be happy to answer any questions. I'm completely stumped though! Thanks!.

bryce.hanson

Bump! I'm thinking Air Flow Meter???

James Bailey

When did this problem start ?? and were all the changes done as an attempt to fix it ? Have you tested the fuel pressure to the injectors ?

85euro928

I'm just throwing this out there...
If it's running so rich that it stalls then it has to be getting A LOT of fuel, more than I think high fuel pressure would cause right? I've run my fuel pressure up to more than 60psi and it didn't cause this condition. What about a short to ground in the fuel injector wiring harness, or something along those lines? Could it be that the injectors are continuously firing? Maybe you have a bad LH that's causing excessive fueling? Have you done a search here on RL? Did the car ever run right or did you buy it in this condition? (just rambling).

linderpat

be very carefule of dumping a lot of fuel into the cat, especially with the car in the garage. Keep an extinguisher handy. I don't know what the problem is, however.

bryce.hanson

Hi guys,

Thanks for the replies!

I bought the car like this. So far I've sent in the ECU for repair, replaced the cold starter, replaced the fuel pressure regulators and fuel dampener, new fuel pump relay, new fuel pump, new fuel filter, ran with or without O2 sensor plugged in, and had the injectors cleaned/tested.

The fuel pressure has been checked by a Porsche mechanic I know. He said the fuel pressure is perfect, and the injector pulse is good.

I should have added this to the video as well,

If the car is running without the fuel pump relay plugged in, right when I plug the fuel pump relay in the car dies.

bryce.hanson

And Linderpat, I have a huge *** fire extinguisher near by. Just incase.

Landseer

Is it a new oxygen sensor?


The two 84 USA cars in my stable both ran very poorly, with very low MPG, with their old (Original?) o2 sensors.

Also, who specifically rebuilt your 84 USA brain?

IcemanG17

temp II or temp I inside air flow meter....on my old 928 Estate it was VERY sensative to even slightly out of spec readings for both temp sensors..... Here is a test if the car is running like crap, pull temp II and bridge it with a small piece of wire and see how it runs....this simulates VERY hot weather....when they fail they fail to RICH....

I did have an AFM that temp I was just slightly out of spec..only a few hundred ohms....ran like crap...changed it....PERFECT

yaskota

I totally second Iceman's recommendation!

My 84 US S (L-Jet) was running über rich November to February, back firing and all kinds of naughty stuff (had to feather accelerator to keep her from dying during drive home!). And this when I finally took possession of her *after* the seller (not a PO) had taken... well about four months to troubleshoot it and had only replaced (the remaining) 4 injectors!!!

Before any work by me or since purchase in November, seller had installed (the first four) injectors, new plugs, fuel pump, fuel damper, two fuel regulators and messed with- oh I forget what it's called- idle control? (crazy long screwdriver & should have been monitoring or measuring, but he did it blind!)

Anyhoo, since February, I've installed new plug wires and green wire & messed up timing in the process. In taking it in for professional help, they had timing correct in moments, replaced temp sensor (II? top front of my 4.7L). Since this (early May), idle has been solid at 750 rpm.

As another new-to-me '84 owner I should add that since then- for engine work- I've needed a new Ignition Coil (early June), cleaned & refurbished CE panel, replaced all interior bulbs (minus POD which will happen later this month), and am 1/3rd of the way into cleaning ground points. YEMV.

Chasing electrical gremlins that has my dash voltmeter sunk & Battery not charging (by alt.), I just installed a new AGM battery and between now and Wednesday, I will either be able to get my car up to take a look at my alternator & hope I find something obvious (from possible driveway scraping) or have a rebuilt one installed on Wednesday.

Also- I'm very curious which '84 you have!

-tom

Btw- if you haven't already had your VIN checked for option codes, I highly recommend it! (Search for "Official VIN & Option Request" thread... also listed in FAQ/newbie sticky).

bryce.hanson

Okay sorry it's been a few days guys! So what I've tried so far

Replaced the FPR's and dampener. I also tried using the brain out of my buddie's 928 (His is an L Jetronic as well) and I came up with the same result. I disconnected the O2 sensor and it's not running rich anymore, so that's good. However, the car will ONLY run if the fuel pump is not running. I plugged the fuel pump directly to the battery with a toggle switch. If the fuel pump is off, it runs great, but the second I turn the toggle switch on, the car dies. very strange I'm going to try a few things, double check the fuel line etc and get back to you guys if I figure it out.

James Bailey

Trying to remember if you can incorrectly put the dampener on the rear of the fuel rail in place of a pressure regulator....too lazy to go look under the hood of the old very brown 1980 never installed PET on this computer !

bryce.hanson

Nah not possible, unfortunately. :/