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93 240 cranks but won't start

Help, Advice, Owners' Discussion and DIY Tutorials on all Volvo's "mid era" rear wheel drive Volvos.

1975 - 1993 240
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jmlmr2
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93 240 cranks but won't start

Post by jmlmr2 » Mon Jun 20, 2016 8:25 pm

long-time forum lurker, first time poster...

My '93 240 recently began intermittently shutting off while driving. While driving normally, with no symptoms of anything out of the ordinary, the car simply shut off 3 or 4 times over the course of a week or so. Cycling the key a few times in the ignition didn't seem to do anything - it would crank and crank but not start. It felt like an ignition cut when it shut off (engine didn't sputter - just shut off like I had shut it off with the key) so I pulled/replaced the low voltage wires to the ignition coil, after which the car restarted each time. I therefore suspected the coil of being bad, and running the diagnostic tests found that the resistance values were out of spec, so I installed a new coil. The car started right up with the new coil. Just out of superstition, I shut it off and attempted to restart, but it just cranked and cranked. Hmm.

I checked and verified spark at the plugs. In cycling the key in the garage I eventually noticed that the fuel pump relay wasn't clicking and the fuel pump was not priming. I checked the #4 fuse and found no voltage with the key in "run". I checked the main fuse attached to the positive battery lead under the hood and it tested good (continuity across both poles of the fuse). Next step was the fuel pump relay. The lead from the battery shows +12V, but (here's where it gets weird...) the terminals that are supposed to be +12V with the key in "run" are reading 0.3V with the switch in "run". The readings at each terminal are the same with the relay inserted or removed from the socket.

I'm not sure where to go from here. Is there a way to test the ignition switch to see if that is the culprit before dropping $100 on a new switch? I'm not sure what else could be causing the odd voltage reading at the relay. I've tried jiggling the key around in the switch with the multimeter in the switched wires running to the fuel pump relay but didn't observe any variation in the reading, but if something is completely broken off inside the switch maybe that makes sense?

Any help would be appreciated - even just other things to check that I might be missing. Thanks!

harryhendo
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harryhendo

Re: 93 240 cranks but won't start

Post by harryhendo » Tue Jun 21, 2016 6:14 am

Well you've taken a very methodical approach to the problem so far... good work!

The engine needs fuel, air, and spark to run, and you seem to have eliminated the spark problem. For fuel:

1) have you replaced the fuel filter recently? This is a maintenance item that is often missed, and causes an intermittent fuel starvation.
2) when you turn the key to ON, do you hear the fuel pump "spool up", i.e. turn on for a few seconds to bring up pressure? Have an assistant listen when you turn the key to on. If no whirring sound, then the fuel pump may be flaking out and needs to be replaced.
3) if the fuel pump runs, do you see fuel pressure at the fuel rail? The fuel pressure regulator (small brass or dun colored device at the end of the injector rail with a vacuum hose going to it) is a common culprit for lack of fuel or poor starting. I crossed referenced the volvo regulator to a Motorcraft part that I found on rock auto for $20.
'92 940
'94 855 (manual!)
'00 S70 (manual, the $500 experiment)
'02 V70

jmlmr2
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Year and Model: 1993 240
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jmlmr2

Re: 93 240 cranks but won't start

Post by jmlmr2 » Tue Jun 21, 2016 7:32 am

I haven't checked the fuel filter, but didn't really suspect it as the cut out was immediate - no symptoms of partial fuel starvation, just went from running 100% normal to shutting down completely. This led me down the path I'm taking of looking for electrical faults (as a first course at least).

The fuel pump is definitely not running when cycling the key to "run". I have the strange 0.3V signal going to the fuel pump relay harness (where I should have 12V with the key in "run"). I can get the pump to run by jumping the red wire in the relay harness to the yellow/red wire in the harness, but even with the pump running the car will not start. I can definitely hear the pump running, though I haven't pulled a fuel line to verify that fuel is getting to the injectors. To me, this points to an "upstream" problem, as the signal voltage to the fuel pump relay is getting fouled up somehow. Does anyone know the signal path from the ignition switch to the relay? Does it route through the ignition and/or fuel computers prior to hitting the fuel pump relay?

Thanks for the help so far!

harryhendo
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harryhendo

Re: 93 240 cranks but won't start

Post by harryhendo » Tue Jun 21, 2016 11:10 am

The "trigger circuit" for the fuel pump relay comes from the Jetronic (K or LH) relay (6 pin, usually green or white). You might want to jiggle that one around, or open it up and clean it up. The Haynes manual has a schematic, which might be of help. You can find schematics online as well.
'92 940
'94 855 (manual!)
'00 S70 (manual, the $500 experiment)
'02 V70

jmlmr2
Posts: 5
Joined: Mon Jun 20, 2016 8:01 pm
Year and Model: 1993 240
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jmlmr2

Re: 93 240 cranks but won't start

Post by jmlmr2 » Wed Jun 22, 2016 3:59 pm

Derp. Should have already checked the schematic to trace the wiring to the fuel pump relay... That 0.3v reading on a couple of the leads has me baffled.

jmlmr2
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jmlmr2

Re: 93 240 cranks but won't start

Post by jmlmr2 » Thu Jul 07, 2016 6:18 am

ok, so I finally got around to digging through the wiring schematics and have concluded that there is no power coming from the ignition switch (pin 15) blue wire that serves as the trigger for the fuel pump relay. That same blue wire also appears to feed fuse 5, which I also think was not getting power when I last checked...need to verify that. However, assuming that there's no power to fuse 5 and also no power to the fuel pump relay trigger wire, is it then safe to assume that the ignition switch is at fault? There doesn't look to be any other connections between the switch and the fuse panel or harness that connects to the fuel pump relay...

jmlmr2
Posts: 5
Joined: Mon Jun 20, 2016 8:01 pm
Year and Model: 1993 240
Location: SE PA
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jmlmr2

Re: 93 240 cranks but won't start

Post by jmlmr2 » Wed Aug 24, 2016 10:38 am

In case anyone stumbles across this post looking for a resolution, it ultimately turned out to simply be the fuel pump/injection relay. There was a hairline crack in the circuit board that was causing the intermittent fault (if I was able to get the car to start, gently squeezing the relay would cause it to cut out or shut off completely). New relay and, as Edd China would say, "job done".

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