I pulled fuse number 4 and 7 (because I've seen conflicting info on which fuse) on my 1988 240 and it's still idling after 15 plus minutes. Shouldn't it have stalled out long ago? I beginning to wonder if someone bypassed the fuse somewhere along the way.

Anybody have an idea of how long it would normally take to stall the car out?

Update: after 45 minutes and having pulled many fuses out to see if it was just mis-wiring the car still ran. I unplugged the fuel pump relay and it stalled immediately. Can I accomplish that same thing (emptying the fuel system this way)?

 

What are you trying to do besides discovering ways to stall a 240?
If you cut off the fuel the engine will stop: that's how they stop diesels and jet engines since they have no continuous ignitions to speak of. Gasoline engines normally stop by shutting off the spark but shutting the fuel also works and that makes them sputter....

 

I want to replace the in-tank fuel pump.

 

It should stall out in just seconds. This is a method for depressurizing the fuel rail. However, it shouldn't be necessary to depressurize it to replace the in-tank pump as it doesn't generate much pressure. The pump under the car is the one that pressurizes the fuel system.

Fuse 6 runs the main fuel pump. If you pull it, turn the key to the II position and you can hear the main pump run, then someone must have bypassed the fuse.

 

Thanks. I've concluded that someone did bypass it. At one point I had fuses 4-9 all out at once with not affect. I wanted to be safe and avoid having fuel drain out of the lines to the rear pump when I disconnect but I will just work around that.

 

Where the hoses connect to the tank is the highest point of the low-pressure side of things, you shouldn't have any problems with losing much gas when you disconnect the lines. There should be no pressure since the pressurized system has a check valve that should keep gas from flowing back. The return line from the fuel rail is also low pressure and should not have any pressure on it when the engine is shut off.

 

wait, I thought the main pump was only on the 25A main fuse under the hood, and that the TANK pump was on fuse something-or-the-other. the car will run with just the main pump.

 

Well, that would certainly explain it although the chart on the inside of the fuse box cover indicated fuse 7 was for the main fuel pump and I believe 5 was for the in-tank. On our 91 sedan, fuse 4 is for the main pump and that definitely will stall the car.

If what you were saying is true that would make a sense of the experience. It's embarrassing enough when you are having a hard time starting a car but when you can't make one die, that's darn right humiliating.

 

ok, looking at the 87/88 240 wiring diagram now. fuse 4 is the tank pump. fuse 7 isn't even part of the fuel injection system, its... hah, brake lights.

the 25A fuse under the hood powers the entire fuel injection system, via the fuel pump combination relay

 

ah, fuse 6 is the main fuel pump and stuff.. on K-Jet CI cars circa 1987/88, none of which were sold in the US. I'm assuming this car is a US model LH2.2 car, hence what I wrote above.

 

What you're saying must be correct based on my experience but the decal on the inside of my fuse box cover says for fuse 5 (in-tank fuel pump) and for 7 it says (main fuel pump). I'm looking at it right now although between 1988 and now it (the fuse box cover) could easily have been switched. Other fuses on that diagram did match.

Thanks for the info.

 

here's what the wiring diagram for the 87/88 says...

1 - cigar lighter, tailgate wiper, power mirrors, radio, antenna
2 - windscreen wiper, horn, headlamp wiper
3 - heater fan
4 - tank pump for fuel injection
5 - light switch, day running lights, dim-dip (UK)
6 - main fuel pump (CI/K-jet only)
7 - Brake Lights
8 - Courtesy lighting, clock, trunk light, engine compartment light, central locks, electric antenna
9 - hazard warning lights, gear shift indicator
10 - power windows
11 - overdrive, heated rear window
12 - reverse light, power window relay, ac, switch for heated rear window
13 - control unit (diesel), direction indicators, seat belt reminder, solenoid of diesel fuel valve, hot start valve, PTC resistor
14 - rear fog lamps
15 - left parking/tail lights, number plate lights
16 - right parking/tail lights, instrument and control lights, indicator lamp, parking lights

its possible your fuse cover is off a different year car?

 

Pierce, all three of the manuals that I have say to do exactly what jsmiled did, BEFORE you work on anything to do with the fuel system. I tried doing just that, myself, and got the same result as jsmiled. I, however, had also read you and others say many times that there won't be much fuel squirt out any darn way. So...

JSmiled, I recommend that you just ignore the warnings about fuel squirting out. When I replaced my in-tank-fuel-pump no fuel squirted out at all. When I disconnected things up front, I only got maybe a tablespoon of fuel squirting out. Really not worth worrying about unless you have wads of newspaper in your engine compartment and you work by candlelight.

I honestly believe that most of the diagrams are just dead wrong. They are all copies of copies of copies that were then scanned and stuck in books that publishers churned out as fast as possible with as little actual double checking as possible (because all that stuff costs money). Have you seen the electrical diagrams in the Bentley manual? They are almost unreadable. The diagram that keeps getting passed around for the fuel system for the LH 2.4 for 1987 - 1993 240s (the same diagram you sent me, Pierce) is drawn so that it is hard to tell whether the main pump is connected after fuse 4 or before it. Everybody keeps saying over and over again that fuse 6 is for the main-fuel-pump but, according to these diagrams, it is for the entire fuel injection system, the ECU, the injectors, everything. So, yes, it is for the main fuel pump too but most certainly NOT JUST the main-fuel-pump.

So, removing fuse 6 will kill the engine, but that is not because it shut off the main fuel pump and the pressure in the fuel lines ran out. That is from simply shutting off the entire fuel injection system altogether. Removing fuse 4 will just make your car run crappy but will never kill the engine if you are just sitting there idling.

What all this tells me is that the whole spiel they print in the books about relieving the fuel pressure by pulling fuses and waiting for the car to stall are total bull****. Just something they stuck in there to make it sound as if they are looking out for your safety and to take up space.

I even think the labels on the fuse-panel-cover are wrong too. When people keep repeating that fuse 4 is for the in-tank-fuel-pump and fuse 6 is for the main-fuel-pump (just because that is what it says on the fuse-panel-cover) that is misleading because fuse 6 is not ONLY for the main-fuel-pump. Fuse 6 is just as much for the in-tank-fuel-pump as it is for the main-fuel-pump.

If I am sounding a bit frustrated it is because I am. One would think that for a 20 year old car that was this popular, that there would be reliable documentation about them available. Yes, there are the Green Books, but they aren't available any more except on dvd. And I still don't know how well one would be able to trust even them. So all of us are stuck guessing and scratching our heads.

 

the fuel squirting was a bigger problem on CIS systems where there's a fuel accumulator, and the fuel pressure is higher.

87-88 240s are LH2.2, 89+ are LH2.4 and occasionally LH3.1.

I have the Volvo factory "green book" diagrams for almost every year on an OTP DVDrom, these are the factory schematics. they are very clearly drawn, although some years the OTP scans are kinda awful. the greenbook schematics are the ones with the main power lines in red.

fuse 6 goes nowhere on an LH car, its not connected to the fuel injection at all, its the main power for the K-Jet/CIS system used in the 70s up to 82 or so. The LH 240's use a 25A fuse under the hood for ALL of the fuel injection system. this power goes to the double relay, and one half of that relay powers the ECU and stuff, while the other have of that relay powers the fuel pumps. only the tank pump is on fuse 4 (which is after the fuel pump relay hence also on the 25A fuse).

 

Yes, definitely. In fact, after your feedback and checking around online, I think the diagram It has on it is from a 1986. This has a 1986 engine in it and a few other interchanged parts but because the fuse box cover was the same navy blue as the interior I guessed it belonged.

I scrapped the project for yesterday and will try again. I picked up a new NAPA brand pump for only $38 that may be a little under powered than some but since the car does run on only the front at this point, I'm hoping that any help from this additional pump will just be bonus. I will post how it works out since it's a relatively cheap solution.

 

Thanks and I have learned to take with a grain of salt what I read online. I am planning to try to avoid having to buy a new gear puller by attempting to open it with some light tapping with a hammer and punch so I didn't want any spillage at all in case I generate a spark but I may just spring for one anyway since both of our 240's really need new in-tank pumps so I'll be doing it twice.

 

Wow, a lot to do about nothing.

I just open any point of the fuel system and put a rag around where the opening is, a little gas comes and soaks a little bit of the rag!

I little bit of practical experience doesn't hurt...

 

Oh, I wouldn't use a metal punch. That will just bend up the ring. I got a 3/4" hardwood dowel, cut it in half, and used that instead of a punch. Keep your saw handy and, as the end of the dowel gets beat up, just cut off the beat up part and keep going. It took me a little while but I still had plenty of dowel left when the ring finally came loose.

 

That's what I do too. Use something to hammer the bung ring off that's not too hard that it damages it beyond future usefulness: could be a dowel, another piece of wood, something soft yet hard enough to get purchase on the ring.

 

when we changed my tank pump on my '92 745T, the ring flat out would NOT go back on, kept popping off the threads long before it could be tightened. it had sat off the car for a few days while we got additional parts we needed... I think I should have put the clamp back on the ring and tightened it while it sat so the ring would be kept in correct shape. ended up buying a new ring (which wasn't that expensive but took a week to arrive).