Ever since I had my fuel pump replaced my gas mileage went from 16 miles a gallon to 8 miles a gallon slowly, now my car failed emissions co idle reading was 4.23 percent limit is 1.20 percent. I replaced the catalytic converter two years ago I don't think that would have anything to do with the gas mileage. Volvo dealership wants 195 dollars just to run a diagnostic test on the fuel pump I'm looking for any and all suggestions the gas mileage has been Driving me crazy for a long time please help, thank you

 

Hi COs says the car is running rich - as does the poor fuel economy. Is this a turbo or NA car? Any check engine codes? Lots of things can contribute here - poor spark, low compression, faulty fuel metering (too little air, too much fuel). What tests have been done so far and what parts are new and what are suspect? Start by inspecting the plugs - are they all black and oily or just a few? Has the fuel pressure been measured? is the intake air path clean and clear? When you did the cat, I assumed the O2 sensor was done - is there any wiring issues there? Any intake air leaks/torn tubes/hoses, exhaust leaks, tail pipe crimps? My point here is there's a lot of things to inspect and test. For $150, you should be getting a full hour of diagnostics - which should include a bit more than testing the fuel pump. Perhaps you should ask to speak to the shop foreman about what his plan is for the hour of diagnostics.

 

I was going to replace the plug wires today sometimes it seems like it's missing I'll pull the plugs and have a look at them only new parts is the fuel pump and it was after it was replaced that my gas mileage started going down and down my mechanic said it was because I wasn't burning premium gasoline and I knew that wasn't true because I was burning 87 octane before he told me to come by his shop and he'd pour something in my gas tank, that would be like putting a bandaid over a gash I'm not sure how to reply on this site I've never been on it before but I appreciate your response

 

you can reply using the brownish red Reply button or scroll down for the quick reply. Gas octane has nothing to do with the air/fuel mix. All premium does is gives you resistance to ignition under compresssion (ie pinging when accellerating/going up a steep hill etc). Most Volvos have knock sensors and run fine on 87. Brand name premiums also have a bit more detergent as well - Consumer Reports did a test and showed a tank of premium can reduce some deposits same as adding a can of Techron and then you are good to go for another few months so you can drop a can of injector cleaner from time to time or run a tank of premium once a month. Air intake leaks are often difficult to find and may require a shop with a smoke machine but you can start by doing your own visual and spray around connections/seams/pipes with some carb cleaner to see if any gets sucked in and bumps the idle. If you don't know the quality of your ignition, a "stage 0" tune is a good investment - cap, rotor, wires, plugs, air filter to start.

 

thank you for your time and advice

 

My mechanic finally decided to move into action after my car failed another emission test, he replaced a sensor in the computer, replaced the plugs, you were right, they were all black, and he said he changed the oil because he said the oil had gasoline mixed in with it, is this common? Anyway I'm in Oklahoma on vacation and will be back in DC Monday night, I hope that my car passes emissions this time, it's a ticketabl offense to park your car on any street in DC with an expired sticker. Will keep you informed on what happens at inspection station

 

He replaced the fuel pump and the computer at the same time Last year, and every since then the bad gas mileage and I could also smell gas all of the time so it would make sense to me that the computer had a faulty sensor in it from the start

 

I hope you're still keeping up with this, well I got back from Oklahoma and picked up my car took it to the inspection station and the CO numbers had went way up and now my HC failed also so my mechanic didn't do anything but make matters worse the Volvo dealership didn't want to work on it because they said if they broke something on it they wouldn't be able to get parts for it but they did reccomend a place called the Volvo Specialists I just dropped 250 at the other mechanic and the only good thing I think he did was change the plugs I will keep you updated

 

You DO need another mechanic for sure, one who knows older Volvos! Your Volvo is running too rich, lots of unburned fuel causing problems--could be several reasons, hard to say after all that has been done... Replacing computer, pump, etc, steps need to retraced to make sense of it all.

 

The new mechanic called yesterday and said they needed a thousand dollar deposit, the fuel regulator the other mechanic put on was the wrong one and you're right they're having to retrace all of the steps he did, the light that gives off the codes was disabled and they said there were four codes all dealing with the fuel delivery system bad o2 sensor bad and wiring wrapped around the exhaust system and needing rewiring these guys really seem to know what they're doing wish I'd taken it to them two years ago when my other mechanic put a fuel pump and fuel rail on car will keep you posted

 

Well the car finally passed emissions with flying colors, they basically did what the other mechanic had did two years ago but put the right parts on, they replaced the fuel rail with one for a Regina system, it had one for a Bosch system on it and replaced the 02 sensor and replaced the check engine light, which I wish they would've contacted me first , I would've let that slide. The total bill was 1,653.00 I feel like they really stuck it to me. The odometer doesn't work so it's hard for me to tell if my gas mileage has improved, they told me it would cost 1,200 to replace the odometer system, do you know anything about replacing the odometer in these old volvos? Anyway I spent 1,900 getting the car to pass inspection and the car is no where near worth that. I wished that my odometer worked so I could tell what kind of gas mileage I am getting, thanks again

 

Yeah, that's steep, but that's what happens under such scenarios. I can't see keeping an old Volvo under these circumstances unless you do the work yourself which is not feasible for everyone.

Your speedo problem is common for '91-'92 models. You can have it repaired, it usually takes replacing some diodes; hard to get a used working one anymore, so best bet is to get yours rebuilt and swap it in.

 

Do you know who I could contact about getting my speedo rebuilt? They also replaced the manifold gasket, it was cracked in half.

 

https://www.instrumentclusters.com/speedometer-repair
Try this, I have no personal experience with guys...