'91 740 fuel pump or mass airflow sensor

dani · Post by **dani** » 25 Jun 2010, 19:34

Hi guys - back here again. I left off with you a couple months ago with this thread:

https://www.matthewsvolvosite.com/forums ... 1&p=125470

In short, the car has been bogging on acceleration pretty badly. To add to this, there's been some new developments - one, there's been a loud rattling sound in the back (exhaust?) when I'm idling, and two, the car has about a 30% chance of starting up on the first try. Sometimes it starts fine, other times it takes two or three tries to get it to turn over. Sometimes it starts and promptly stalls.

As recommended on the original thread, I checked the transmission fluid, it was pretty low, so I added some. Bogging was still happening, so I brought it in to the mechanic and he replaced the air intake boot, which to my relief was a pretty inexpensive job. THAT was great, however, the problem didn't go away, and it actually got worse - to the point where I couldn't get the car to accelerate over 30mph (struggling to get it to really move at all) and had to get it towed home.

The car's been waiting at the shop this week, and my mechanic just left me a message tonight saying it looks like it's a bad fuel pump or a bad mass airflow sensor. No estimate though. What I'd like to know is....can anybody tell me how much each of these repairs should cost? I have no idea what kind of range is normal for this, and if he quotes me high I want to ask around at other shops. Do you guys think these bad parts are the problem?

Any info on this would be appreciated! I'm so tired of paying for expensive repairs, so I want to make sure it's being done right. Thank you!

Post by **billofdurham** » 26 Jun 2010, 10:03

Replacing the main fuel pump has a book time of 0.4 hours (approx. 25 mins). The in-tank pump has a book time of 1.1 hours and the MAF has a book time of 0.2 hours. None of them are high cost labour jobs.

Bill.

Retired MVS Contributor · Post by **Retired MVS Contributor** » 26 Jun 2010, 15:54

I have the same Volvo...It has the Regina fuel injection system and does not have a MAF...The MAF is used in the Bosch LH-Jetronic system...Near the left front, next to the alternator, is the large black air intake tube...The air temperature sensor is located on the inboard side of this tube...Near the firewall, also on the left side, on the strut brace, is the diagnostic unit, and right next to it on the inboard side of the brace is the pressure sensor...These two units (temperature and pressure) take the place of the MAF...There is a small white plastic vacuum hose connected to the pressure sensor from underneath...It might have pulled off...

dani · Post by **dani** » 26 Jun 2010, 20:34

Okay, good to know. But if I have a mechanic do this, how much do you think it should cost? Parts and labor? I'm a 23 year old girl who knows nothing about cars, so I can't fix anything myself!

Kirby J · Post by **Kirby J** » 30 Jun 2010, 15:11

I have a 93 940 w/ the rex/regina fuel system and am experiencing similar problems. I have replaced both the MAP sensor and the air temp sensor,engine temp sensor, plugs, plug wires, dist cap, radio supression relay, fuel filter, air filter, cleaned the throttle body, replaced the TPS switch, cleaned the air idle motor, and even did a visual inspection of the Cat Canverter. The car still hesitates severely under load. So when you find out what this is please tell me too!

Kirby J