Help! IAC causing no start in ‘93 940

[swedishsledmafia]

I linked the two pins in the right order, tried it a few times with somebody listening outside of the car. A distinct click could be heard from the gas tank, as well as a click from the front of the car. The click repeated whenever I’d take the wire out and put it back.

As far as I know, healthy fuel pumps make a whirring noise. I’m not sure what the click means. I wanted to turn the car over with the jumper wire in just to see if it would start but probably not a good idea if all the rest of the relay connections arent in eh.

Thanks again, hopefully I’ll get to the bottom of this Volvo absurdity soon.. 😂

[Laird Scooby]

Sounds like you have two pumps in that case, first thing to do would be confirm that by looking underneath.

It's unusual for both pumps to fail simultaneously so i'd look at the fuel pump relay. The clicks could be from fairly quiet pumps kicking into life but the acid test is to run a pair of jumper wires from the battery and feed the pumps direct.

The main one underneath has +ve and -ve markings on, the one in the tank can be fed by opening the tailgate, lifting the cover off the left hand cubby hole between the rear light and wheelarch and locating the 3-way connector that feeds the pump.

The 3 wires will be pink, black and another colour i can't remember just now. The pink is +ve to the pump, the black is -ve or earth if you prefer. Whatever you do, DON'T connect +ve to the thrid wire - this is the wire from the sender unit to the fuel gauge.

In both cases you should hear a whirring from the pumps, if not tap the main one underneath with something heavy ish with the power applied and see if it starts. For the in-tank pump, keep the power applied and tap the bottom rear end of the tank with the palm of your hand - again if it starts working you know it's a pump problem.

[TonyS9]

Originally Posted by Laird Scooby

That's only for the self-test on start up Tony. When it throws the code as a result of a "dynamic" fault, it means the engine hasn't responded to the AICV action that the ECU expects.

In this case it is expecting to see the engine speed increase which hasn't happened for another reason (lack of fuel pump action perhaps which may be due to the CPS not giving a signal) but still throws the AICV code as that's the only one it has "evidence" for.

Are you sure about that? That means when you squeeze the IACV pipe closed to test the throttle body adjustment if would throw a fault. It doesn't seem to.

The error code reported was 'signal missing from IACV'. Remember that a signal is mostly "outputted" to the IAVC. The ECU is just checking there is some current demand.

LH2.4 doesn't seem to check for idle range, it is fairly well indicated and could theoretically be caused by bad driving/operation in a manual. The Motronic does seem to have an error code for it. Ie there is a code listed in the 940 FAQ for idle range but is not applicable to LH2.4.

It would be very problematic to try a make an error detection based on engine speed feedback from changes in the IACV. You would need to know the load situation at all times and the AMM is just too slow and insensitive for idle.

[Laird Scooby]

Originally Posted by TonyS9

Are you sure about that? That means when you squeeze the IACV pipe closed to test the throttle body adjustment if would throw a fault. It doesn't seem to.

The error code reported was 'signal missing from IACV'. Remember that a signal is mostly "outputted" to the IAVC. The ECU is just checking there is some current demand.

LH2.4 doesn't seem to check for idle range, it is fairly well indicated and could theoretically be caused by bad driving/operation in a manual. The Motronic does seem to have an error code for it. Ie there is a code listed in the 940 FAQ for idle range but is not applicable to LH2.4.

It would be very problematic to try a make an error detection based on engine speed feedback from changes in the IACV. You would need to know the load situation at all times and the AMM is just too slow and insensitive for idle.

Good points there Tony and the reason why squeezing the AICV pipe is that it reduces airflow through the MAF and the mixture stays the same so i'm guessing provision has been made for the ECU to not throw a fault in this situation - likewise unplugging the AICV to check/adjust the base idle speed (where possible) doesn't throw a fault either.

In many respects the Bosch stuff is fairly forgiving of certain things but exceedingly fussy on others, no sense of consistency on it.

[swedishsledmafia]

Thanks for the super detailed write up! Seems like it might be only the one pump, I looked but couldn’t find the in line pump for the life of me. Anyway - hooked up the wires to the 3 way connector for the in tank pump and heard nothing. Tried smacking the gas tank too, and nothing. This must be pretty telltale that it is in fact the pump that’s gone bad I’d say.

[Laird Scooby]

Originally Posted by swedishsledmafia

Thanks for the super detailed write up! Seems like it might be only the one pump, I looked but couldn’t find the in line pump for the life of me. Anyway - hooked up the wires to the 3 way connector for the in tank pump and heard nothing. Tried smacking the gas tank too, and nothing. This must be pretty telltale that it is in fact the pump that’s gone bad I’d say.

Sounds fairly definite but asking a potentially daft question, you did connect to the correct side of the 3-way plug? The pump cable heads off towards the spare wheel well and the car side goes up and over the wheel arch.
Wouldn't be the first time someone has fed the car with the direct feed by mistake.

If in fact it is the pump, welcome to the world of Volvo Gynacology! It's a fiddly job to do and you'll also need a new tank seal from Volvo, usually available same day and relatively cheap.

[TonyS9]

I would have expected a 93 to have 2 pumps. The high pressure pump is normally beside the fuel filter under the drivers seat.

I thought the single in tank pump wasn't until 95.

[Laird Scooby]

Originally Posted by TonyS9

I would have expected a 93 to have 2 pumps. The high pressure pump is normally beside the fuel filter under the drivers seat.

I thought the single in tank pump wasn't until 95.

True but the Volvo diagram for the Regina equipped models only shows one pump Tony. I know they did strange things with Regina cars, thankfully we didn't get any (many?) of them here so we don't have to suffer lousy French electrics!

[swedishsledmafia]

Yeah Regina’s sorta weird all around, the guy who sold it to me said advertised it as a Bosch 😂 wish it was. Damn I think I might’ve connected to the wrong one, my bad stupid mistake. I’ll retry the test with the right connection when I’m back home later this weekend but I don’t expect to have a different result - the fact I haven’t been hearing the fuel pump otherwise after trying to start it all are pretty suggestive.

Either way, once I find out what it is I might just store it for winter and deal with it in the summer. I don’t know if I’ll have the time to fix it right now but I don’t want to give up on this car completely.

[Laird Scooby]

Originally Posted by swedishsledmafia

Yeah Regina’s sorta weird all around, the guy who sold it to me said advertised it as a Bosch 😂 wish it was. Damn I think I might’ve connected to the wrong one, my bad stupid mistake. I’ll retry the test with the right connection when I’m back home later this weekend but I don’t expect to have a different result - the fact I haven’t been hearing the fuel pump otherwise after trying to start it all are pretty suggestive.

Either way, once I find out what it is I might just store it for winter and deal with it in the summer. I don’t know if I’ll have the time to fix it right now but I don’t want to give up on this car completely.

The injection is Bosch but the ignition is Regina - why Volvo decided to try and "mix'n'match" i'll never know but it was never a good idea, especially with units known to be troublesome.

If you retry the test and give the tank a whack under the back end with the palm of your hand while it's powered up, the pump might just start running. If it does it's highly doubtful it will be reliable so if that test proves it then it's new pump time.