Greetings all. A long standing starting problem with my 940 Turbo has finally come to a head. It cranks but will not fire. Just before the problem became "terminal" I became conscious that it was associated with a lack of the normal whirring sound when turning the ignition key "one click."

I understand that this noise may have emanated from a relay.. possibly a fuel pump one. It is normally a very obvious sound and so it may come from under the driver's seat as per the suggestion I found on Fixya. I also experienced exactly the same problem with a friend's US '94 Honda Accord import and it turned out to be an EFI relay.

Someone reported a similar problem also at Fixya and it was a faulty wire. I would like to be systematic in my troubleshooting. Being that I don't understand exactly what happens when the ignition key is turned on I am not sure where to start. Also does this model have an inherent weakness in any of the abovementioned componentry?

Any thoughts greatly appreciated

 

A car needs 4 things to fire. Spark, fuel, air, and compression. Do you have spark?

 

Do you have air?
But seriously... So, you don't hear a little 1-2 second buzz when you turn the key to position II (all dash lights ON?). You should, that's the fuel pump. Open the compartment behind the ash tray and feel for the fuel pump relay, it is the one on the left, middle row of the relay try. You should feel TWO clicks when the key is turned on. If you don't, the relay is bad. It triggers the fuel pump.

If want to be more proactive in your troubleshooting, spray some Starting Fluid into the intake, oh, the Left Side intercooler hose toward the throttle body could be good, and try to start it. If it fires up momentarily you'll know you have a fuel issue.

 

It has done this for a long time now and it seems that once a fuel charge is delivered it is away. Hence I don't think it is spark. Thanks for the reminder.

 

Hee-hee. Gasp no.. someone left a cigarette in my ashtray. Brilliant thanks lev. You are really talking my language here. Yes all dash lights on. Fuel pump relay.. got it thanks. I was prejudging this because last time I had this sort of issue it was an EFI relay.

On that occasion it was a car I was babysitting while my friend Jan was overseas on an ICRC mission. She had thrown $hundreds at garages with no joy. On the say-so of a friend I went in and said, "Just do the EFI relay.. nothing else." That sorted it. I will probably do the same with the fuel pump relay, just change it :-) If I am wrong my philosophy is that every time the car breaks just do all the associated things to upgrade it. (I used to watch the 6 Million Dollar Man when I was a kid).

 

7/9's also have a 'radio suppression relay' under the hood that powers the fuel injectors and some other related stuff. if this fails, no fuel gets into the engine even if the fuel pumps /are/ working.

its pretty easy to test... unplug an injector, switch the key to 'on', and use a test light or volt meter between ground and one or the other pin of the injector plug... one side should be powered when the key is on (the other side will either be near ground or floating). if you don't see this, odds are pretty good your 'radio suppression relay' is toast.

 

Thanks pierce. Maybe this is a good place to start as I am one of those "fortunate" owners whose fuel pump relay is not located with the rest and am yet to pinpoint it although I am sure this diagram would make perfect sense to some. i cannot find the fuel pump relay in my 94 volvo 940. it is - JustAnswer

Can you be specific about where the radio suppression relay is located?

 

Well, the FI relay should be there... If not, hmmm... Still, you DO have one somewhere, and it may be failing so you gotta find it!

The Radio Sup. Relay on the '94 940 Turbo is on the left fender wall right below the wiring bunch, may be a foot back from the battery.

 

94/95 940 NON-turbo Bosch systems have a different fuel pump relay in the relay row farther aft (closest to the fuses), second position from the right, might be marked "M". turbos should all have it in the standard middle row, furthest left, might be marked "E".

the different relay is a simple plain single relay, rather than a double relay, on these 94/95 non-turbo cars, the radio suppression relay under the hood also powers the ECU (on the turbos and earlier bosch systems, the other half the standard fuel pump relay powers the ECU and the radio relay only powers the injectors).

 

let me make that a little clearer...

on all turbos, and non turbos up to 1993, the 'fuel pump relay' in relay panel position "E" is actually a double relay, one half powers the ECU, and the other half powers the fuel pumps. There is an additional radio suppression relay under the hood that powers the fuel injectors themselves.

on non turbo 1994/1995 940, the 'fuel pump relay' in relay panel position "M" ONLY powers the fuel pumps. the 'radio suppression relay' under the hood powers not only the injectors but also the ECU and rest of the fuel injection system.


there, is that better?

 

OK, but the patient is a 1994 940 TURBO, so...

Also, Mr. Vee, make sure you have no air leaks between the MAFS and the throttle body, all that plumbing including the intercooler itself and hoses, have a tendency to spring leaks which allows too much air, which brings in too much fuel which floods the car, etc. Your plugs would be WET with fuel if that was the case...

 

In response to Pierce. turbos should all have it in the standard middle row, furthest left, might be marked "E".

Thanks Pierce. Now I feel I am getting somewhere. Mine is a 94 Turbo.. No doubt it has a position E at least.

 

Interesting thought lev. May I please ask what a MAF(S) is. I know I have a lightly leaky airbox since it shed a few of the fastening clips. Would that make a difference?

 

MAF = Mass Airflow Sensor. on a Turbo, its between the air filter box and the turbo itself.

directly behind the airbox in the foreground of this handy photo of my 1992 740 T wagon...

 

Air leaks BEFORE the MAFS are OK as this is UNMETERED air, leaks after are a NO-NO!
So, do you have that FI relay in positon E?

 

well, air leaks before the MAF mean you're sucking in unfiltered air :-/

if you have the proper FI relay in E then there won't be anything in M. those two are mutually exclusive.

 

Eurecar! Houston we have lift-off in position E.. at least a tall flanker standing behind his front row of shorties (rugby metaphor.. I am a Kiwi). It doesn't look like the easiest swap out however. Does one pull that whole tray out or just grow ET fingers?

 

Mass Airflow Sensor. I knew that.. least ways I recognised the term. Thanks for your pic pierce. It is a comforting thought that when any of us look under the bonnet.. (or the hood even) we all see the same thing. Yours looks like a dear old friend even from 6,000 miles away. (I see it's airbox is missing clips too).

 

re: the relays. unsnap and remove the plastic bezel around the cigar lighter, and there's 1 or 2 small phillips screws exposed, remove those, and the tray with the cigar lighter comes out, for easier access to the relays. I'd avoid moving the whole relay/fuse box assembly if possible, no point in disturbing 20 yr old wiring any more than absolutely necessary

 

pierce the term "super" moderator doesn't do you justice.

Re: "on all turbos, and non turbos up to 1993, the 'fuel pump relay' in relay panel position "E" is actually a double relay, one half powers the ECU, and the other half powers the fuel pumps." A day later it is just sinking in. I have soul-searched over this and here you have it for me in a nutshell. Many thanks for this and the above although I will probably refrain from tinkering until the part arrives from the USA. $14 there.. probably $200 here :-)

As for the radio suppression relay under the hood.. I might just put that one on the backburner. No sense overloading my own relay systems before
it is absolutely essential. :-)