Which pump are you calling the main one? My experience is if the in tank pump doesn't work, Shark no swim.

 

Hi Hawk,

A "mechanic" worked on my car. I ran over some railroad tracks, and the car died. It made no start sound thereafter. A "mechanic" replaced the crank sensor. A few hundred dollars later, he found a loose nut on the battery terminal connector.

Check connections at the battery, and under the triangular black cover above the battery in the spare wheel area.

 

Car turns over but doesn't start (no clicking just trying to catch on - once in a while it just barely starts but immediately quits...battery connections are all good. The external pump is functioning, relays swapped out and checked good with the exception of the LH computer (don't have a spare). How does one check the in-tank fuel pump? Does the 89 S4 have one?

 

Could very easily be LH ECU failure, best diagnosed by swapping with a known good unit (or sending to someone to test).

Try reading JDSPorsche for more info.

 

Hornet,
Disconnect your battery
If you look underneath the back of your car, pass side you will see the tank cover. Takes about 10 minutes to remove. Then follow the fuel line to the tank, the line will attach to a very large "bolt head" with 2 wires connected to it. This wll confirm you have an in tank pump. I'm betting you do and betting this is your problem.

 

Hawk,

Loose connections in that triangular cover area have caused starting problems when it would turn over. Also try holding the pedal to the floor until it starts,... may need to charge the battery. Mine would not fire-up,... just cough some for many weeks,... held the pedal down, and it finally fired up,... problem went away.

Some connector could have jiggled loose even under the hood - SWAG.

Any time is a good time to change the fuel filter.

 

Looking towards the front of car, after cover is removed.

 

What mine looked like

 

A better pic

 

After my fun with an empty tank, and everything seemed in working order, it took an AWFUL LOT of cranking to get it fired up - I was pulling everything back off and double checking, ripping out remaining hair etc, but in the end, I just kept cranking, recharging battery until it caught. If you have gas at the front, and spark, it should run. Of course you have an ECU and MAF etc ro wory about, whereas with CIS......
ho 83 Euro S AT 47k Whiteout

 

Jim, thanks for the pics...tried the continuous crank this weekend...started and then died immediately...dead battery stopped the trouble shooting...will continue to crank, and charge...reluctant to drain full tank of gas but I may have to if it is the internal pump...

 

LH brain swap is in order as a test. Find any 928 owner with 87-91 and do swap.

Also, I had experience with a buddy's 90 928 S4 that would start and run ONLY if he held the pedal to the floor. As soon as he let off the gas from full throttle, which by necessity was pretty quick, it would die. Problem proved to be a loose MAF plug. Reseated the plug and the car has run fine ever since. But prior to discovering that we swapped about every other part in the fule and spark department. so, unpluug and replug in the MAF.

 

Can I get to the MAF plug without removing the manifold?

 

yes, but you need to pull the MAf out to do it. USe a 7mm ring spanner to under the drive clip that holds the MAF at the bottom in the rubber elbow.

Sounds like LH ECU failure to me