If I've suspected clogged injectors, I've been known to run a large can of Seafoam or Techron gas treatment into short tank of gas, and drive the whole tank down to fumes at elevated RPMs (like, leave it out of overdrive on the freeway and drive 100 miles), then fill it up with fresh gas, go home and do an oil change (the gas treatment can leave a lot of burned off crud in your oil). sometimes this has helped, other times it hasn't.

 

Well we made a 60 mile trip today...only one stumble during driving but in traffic he acted up a bit. I am starting to suspect the intank pre pump. Although I thought I got the good one, I am not so confident it is 100% functional. I had replaced the main fuel pump because of buzzing noise. the new pump is buzzing, enough to hear it behind me on the floor while seated in drivers seat. Is the buzzing normal on a good pump? I am thinking it is buzzing because it is sucking fuel through a intermittent pre pump???

The sending unit is marking 1/3 low from full when full.

What do you think. The mechanic that I was going to take the car to here on the Island is no longer in business.

 

You have changed many things but have you changed the fuel pump relay?

 

a dead in-tank pump will make the main pump work extra hard, and yes, be noisy. this will increase as the fuel level goes lower. in /my/ case (1992 740 turbo wagon), I'd have fuel starvation during heavy footed acceleration at higher RPMs where the engine would suddenly bog down but recover when I let off the throttle.

while you're in there fixing the in-tank pump, you can sort out the fuel level sensor (test it with an ohm meter, the values are published online somewhere, and if its off, replace it). Also note, there have been a bunch of reports on forums of NEW sensors and intank pumps being wired incorrectly, best to check this BEFORE you install them, and fix any such problem.

 

That's one of the same symptoms I have Pierce.
Sinarf, I thought a fuel relay was a Go/No Go problem and repair? Should I replace this too?

 

on her 87, I'm suspecting the EFI wiring harness too, and in fact scored one cheaply off craigslist (was a new replacement harness specific to 86/87 240s that had been installed but was still in like new condition), and am procrastinating on installing it. getting the parts that go under the intake manifold in place looks to be the hard part.

 

Topped off the tank and went for windy up and down the mountain ride. The fuel guage came up to full level. The car performed wonderfully on a 60 mile round trip. The new main fuel pump still audibly buzzes. Had one stumble on the freeway coming back that Zoot recovered from without having to pull off the road. Injectors or intank fuel pump? If I go back in the tank, I'll be going with a new new sender and new new pump,hose,filter. If I pull the injectors, I'll look for rebuilt's or new. I want to keep this car for a long time.

 

I'd say do the tank. I've not personally experienced bad injectors on the 5 or 6...eeek....7 high mileage volvos we've had, but had several fuel pump issues.

 

I agree with you Pierce. Who has the closest to OE Sender and pump? Ipd? I suspect the one I bought from my reputable euro parts dude. Most every part has been OE or German from him. I was thinking of the Upgrade pump kit and a new VDO sending unit. I also want a new bung ring/me o ring is 2 weeks old, is the $24 tool worth it?

 

Going back into the tank. suspect rubber hose failure and going to swap out new pump with IPD upgrade kit. I am not sure that the pre pump distance from bottom of tank is correct. I think maybe the pump intake is up too high from the bottom of the sump. Does anyone know how long the top of the sending unit to the bottom of the pump distance needs to be?

 

I had the upgraded intake fuel pump kit from IPD overnighted to the Island. Have not installed. Zoot has been running well for the past couple of days with only a rolling Idle after we come to a stop in the driveway. I suspect that is tied to the faulty VSS in the differential. Fuel gauge about 1/2 tank now...I'm going to run it down to see if the problem returns with the stall out stumbles on the road. (suspected faulty pump and leaky rubber fuel hose) New issue....the temp gets right up tothe redmark....haven't had any cooling issues until now....I'll remove and replace the Tstat, flush radiator and top it off to see what happens. Cars that sit for a year or years,,,gotta love em I imagine some obstructing crud has come loose now that water is actually moving through the system.

 

Replaced the T Stat today...Froze half shut. Ran the car on the highway gain...running better....1/2 tank and the main fuel pump gets louder and I had one loss of power. I am now convinced the intank is faulty or the hose is cracked and sucking air. I'm going in with the IPD upgrade pump tomorrow...we shall see if this solves it....if not I will buy the parts to check fuel pressure to see if it is within spec. Still diggin this car a lot.

 

Ok I think this case is on its way to being closed. I went back into the tank today. I could not find any tears or holes on the old accordion fuel hose that connects the pump to the pickup tube. I went ahead with the upgrade kit installation as planned. The AH HA moment came when I snugged up the top fuel hose clamp from the pump to the pickup tube. With the clamps cranked all the way down, a snug tight fit on the pump itself. On the top clamp on the pick up tube however, was loose enough to be rotated. The ID of the 3/8" line that came with the kit was too large for the OD of the pick up tube. I swapped in a 5/16" fuel hose and it all snugged very nicely. I had replaced the sending unit the day after I bought the car since it was broken and rusted apart. Turns out the OD of the pickup on the replacement sending unit was a bit smaller. SO.....Pierce this does certainly seem like a fuel pressure issue...pinpointed to the air being sucked in from the annulus of the fuel line and pick up tube. Another 150 Mile trip planned tomorrow. We shall see....we have already not heard the main fuel pump whining since the remedy. Thanks for your insistence Pierce.

 

Took the kid to school. Car did fine except for pulling in the driveway the rolling idle came back...This I think is related to the Vehicle Speed Sensor code that comes up on OBD. Runs fine but the main pump (2 weeks new) is still whirling audibly in the car with raid off. I'll run it today to see what happens on a long ride. Are these pumps prone to noise? Could this new pump be on its way out already since I was sucking air from the intank pump? (Assumed diagnosis until after today's long trip).

 

Long trip cancelled...trouble right out of the gates.....stumbling again. I headed to local Vovlo dude. He noticed that throttle body had the idle set screw and told me that the TB was off of an older car. We swapped in a 1990 TB, Idle returned down to normal (has been high since I bought it) and it did run better but still stumbled. He suspects the MAF is faulty as idle goes high when it connect and returns normal disconnected. MY FRIGGIN fuel pump is still buzzing under the car. I am growing very tired of this already. I am seriously considering selling the car and going back to 85-89 4Runners.

 

I have same problem 1990 240 Fast Idle after highway driving. Cycle engin Off/On Clears problem. I also have 311 codes !! I would look into this as the cause, I will do the same. My problem is the microchip in the speedometer. It is not putting out the speed sig. to ECU or Cruise Control. I jumpered the Cruise Control input directly to the wheel sensor and Cruise Control works now but not sure where this signal splits off to the ECU.
When I saw your post all kinds of bells went off in my head !!! The 311 code has to be the wild card since this is such a weird problem. The cycle engin Off/On to clear the problem points to the ECU getting screwed up by some bad input and cycling off/on resets it. I'll bet money its the speed sig. missing. ( I replaced-- MAF, O2 Sensor, Fuel Pressure Reg. and cleaned / checked Idle Air Control valve, Throttle Body and Throttle Position Sensor - all Good but problem remained.)
Thanks
Mike M

 

I have also experienced a bad speedo chip and it does cause the engine to stumble upon coming to a stop. On my car it the engine never died but it would just barely not die when stopping before the idle circuit kicked in.

In my case the problem was the ITT 2115 chip on the speedometer circuit board was bad. Actually the chip wasn't burned out as my speedometer and odometer worked fine. Just the taxi pin on it no longer was producing a signal. It got burned out when my son connected the tach (red/white) wire to the double spade when installing the speedo.

I simply replaced the 2115 chip and it fixed my 311 code and the stumbling issues when coming to a stop.

For the loss of power issue, are you sure that power is getting down to the in-tank pump? Many times the the seal where the wire goes through the top of the sending unit fails and the connection is broken there. Can you hear the in-tank pump running?

 

I skimmed most of this and I don't think that this has been suggested. It could be an animal built a nest in the exhaust or the cat is clogged. The back pressure builds and kills it. You could drop the cat, have a look and or run without it. See how it runs. Something like this I don't think would set any codes.

 

If you do decide to purchase a fuel pressure tester, there is an inexpensive option available at most auto parts stores. They don't last long if used alot, that's why I finally purchased a MAC tools Master Fuel Test Kit. Before I bought this awesome set, I went through a bunch of the cheap ones. They will work for your application though and only run about $35 or so. You may need to purchase a 2ft length of high pressure fuel injection hose to make the connections necessary for testing. As far as testing the vacuum regulator, we just disconnect and reconnect the vacuum line watching for an increase in pressure with the hose off, or just snap the throttle and watch for the same increase. This would allow you to verify whether or not this is fuel supply related. A faulty MAF sensor can cause glitchy behavior if there is a loose connection inside. The engine will run without the MAF(default fuel MAP) and this would be a way of verifying whether that is the issue.

I hear your frustration. Intermittent issues are the worst because you don't know if they are fixed until you drive the car a while. I get to diagnose these issues plenty and they can eat up alot of time. Just be patient and try to follow a strategy so that each possible problem area is eliminated as the cause, until you find the problem. I would say that eliminating fuel supply as a possible cause would be a good place to start. The pump noise can be caused by the rubber mounts being broken or any metal to metal contact between the pump motor and the chassis. I have seen all types of electric fuel pumps be noisy for years and never fail.