Hey there,

My car is firing on just the 1st and 3rd cylinders.

I am assuming that it is time for new/cleaned trigger points. I checked the wiring and it looks good. I am getting good spark and the injectors are new.

Any other ideas before I brave the cold ?? Please don't say it could be the ecu.

Also, I needed a new MAP.now at least it doesn't stink like gas. Found a rebuilt one from Fuel Injection Corp. They also rebuild ecu's, and have the connector in the fuel injection harness.

thanks guys.

Hello,

If you have checked all the wiring at the contact trigger points(look very carefully, it is common to see a single wire strand just barely holding onto one of the metal connectors at the end of the wire) and at the injectors, you may have a damaged contact trigger points set.

The points on this set only send a ground signal, so the contact side usually just needs a wipe with a clean match book cover.

But the rubbing blocks on each point set needs to be lubed during each tuneup and this is often neglected and this leads to wear to the extent that the point set might not open and each point set runs a pair of injectors.

What vacuum sensor do you need?

1970 Volvos came with an "010"(last 3 digits of the Bosch part number), the 1971 Volvos came with a "015", the 1972 and 1973 Volvos with a B20E got a "015", with a B20F and a manual transmission the sensor is a "035 and with a B20F and an automatic transmission used a "054".

The information above applies to 4 cylinder Volvos.

Did you know that the current list price for the one vacuum sensor is almost $3000.00 from Volvo?

I strongly suggest that you have yours rebuilt by Fuel Injection Corp as they charge at lot less than $2800.00 and when I spoke to the owner, he knew about some of the internal workings of this unit and claimed he could fix them.

Eric
Hi Performance Auto Service (formerly OVO or Old Volvos Only)
Torrance, CA 90501

How do I get to the trigger points? Just remove the little assembly from the side of the distributor?

Any adjustment/timing?

The trigger points are held in by two screws. Just gently remove the plug and unscrew the screws. Do not sand the points! Spray a little contact cleaner on them and run a business card or match book between them. These are low voltage contacts. Look at the rub blocks for wear. A little distributor grease on the cam inside the dizzy will help prevent wear.

Installation is the reverse. Unless you had to move the dizzy to get to the screws, you shouldn't have to reset the timing.

Rolfe--71E

yeah,

i got the map at the fuel injection corp for about 370. The cheapest other than that was a new one from don thilbault for 750. The rebiult one seems to be just fine. They also said they would test/fix injectors for about 12 dollars each and seem a good place to do business with.

thanks.

I will check the wires again and keep you updated

best and thanks,

Grease

You can check the trigger points with an ohmmeter from each of the outboard
terminals to the center. Both should pulse on and off as you crank the
engine. Good to take the high-tension coil wire out of the coil while you
do this and DON'T hold your elbow there while you are using the ohmmeter!

Why do you think the MAPSensor is bad?

Sometimes apparent MAPSensor and ECU problems can be remedied by unplugging
the big plug from the computer and plugging it back up.
--
George Downs Bartlesville, Heart of the USA!

yeah, I spark myself enough just pulling the plugs!

I didn't know that about the big plug from the ecu, thanks.

the map sensor diaphram was cracked, and i did get a good rebiult one. I feel I have narrowed things down to the ecu and the trigger points, I hope that is the case. I read that two cylinders not firing is generally a symptom of bad trigger points. My car has over 300,000 on it, and have changed about everything but the trigger points, so I am hopeful this is the problem. The only thing left would be the ecu.

enjoy the rest of the weekend.

grease

While you're checking the wires, check all of the Grounds. Especially the injectors. BT

thanks for all the help Brickboard.

The trigger points were bad, and the connection to the ecu wasn't good. She is running great and I am looking forward to spring again.

Now, I just need to find some of the posts on rust!

best,

Grease