The V8 Owners Forum -

Hi All
New to the forum.
I disconnected my battery on my 1991 D1 3.5 efi to charge it and when I reconnected the battery she won't start.
Cranks over and I have good spark at the plugs but will not fire.
How do I check for fuel, I don't know anything about the efi system?
It doesn't have an alarm so I don't think it's an immobilizer issue.
Cheers Simon

Any idea which of the EFi systems is on there?, flapper or hotwire?

Chris.

Assuming Hotwire (as it’s the only one I know anything about) does the fuel pump run for few seconds on power up, you can normally hear it.
If so can you tell if it re-starts when the engine is turned over? As soon as you get a spark the pump should re-start, if not then the EFi is not getting that signal, the ignition is THE signal to make the system perform fuelling without it there’s no chance.

How do I tell if its flapper or hotwire??

From memory
The Hotwire system has 3 relays, one of them powers the fuel pump, I know I needed to replace that relay once.

There is also a black wire that goes to air flow meter, if you bumped that off by mistake the engine will not start.

Ian

V8kiwi wrote: ↑Sat Jul 31, 2021 5:18 am How do I tell if its flapper or hotwire??

If it is 91, it won't be flapper. But not sure when GEMs replaced hotwire.

DaveEFI wrote: ↑Sat Jul 31, 2021 8:49 am

V8kiwi wrote: ↑Sat Jul 31, 2021 5:18 am How do I tell if its flapper or hotwire??

If it is 91, it won't be flapper. But not sure when GEMs replaced hotwire.

Good point Dave, '91 is firmly in Hotwire teritory.
Other than that, difficult to explain without pictures, plenty of photo's on the Internet though.

Ian Anderson wrote: ↑Sat Jul 31, 2021 7:03 am From memory
The Hotwire system has 3 relays, one of them powers the fuel pump, I know I needed to replace that relay once.

Hotwire has 2 relays specific to the EFi function, main and fuel pump, there are a few more but they are related to air conditioning mainly, they won't stop fuel running. About 3 of those, can't remember for sure as I don't have AC

If the fuel pump is firing up for 2-3 seconds when ignition initially switched on then both must be good.

Ian Anderson wrote: ↑Sat Jul 31, 2021 7:03 am There is also a black wire that goes to air flow meter, if you bumped that off by mistake the engine will not start.

Ian

Cable going to flow meter has 4 (I think) wires, I suspect you possibly meant the single black/white wire going to the coil?

Yes. If it's like the flapper in that respect, a white/black wire goes from the coil negative via a plug-in inline resistor to the ECU. If that connection is bad it won't inject.