340 1.4 rough ans slow idling

[Clan]

Originally Posted by Laird Scooby

I thin you had it right the first time! I've known a few Renix failures after 3-5 years, they didn't fare much better in the 400 series Volvos or the Jeep Cherokee (and associated models) and was quickly dropped by Chrysler-Jeep as they were at the time.

Also in the 7/9xx models, the Renix was fitted, if memory serves we didn't get it in the UK but they did stateside and gained a bad reputation for failing quickly hence Volvo reverting to the Bosch system.

The 400 didn't use the same system they had a proper ECU , the coil part was just a switching unit which was pretty reliable .
I have 2 spare coil units for a 400 . and an ECU and electronic carb
for a B 18 U .

Generally the Renix was very reliable if you owned a 340 but as the years went by a sudden failure was not unheard of if you were in the business of repairing the cars ..

[Clan]

Originally Posted by Two340'sman

I have (amazingly) found the Renix unit that I removed from a working 1.7 340 GLE. I ran the car for about 10 years. It was very dirty, cleaned it up a bit.

Strangely, it's marked with 360. Couple of pics.

Removed from 1.7 by A60man, on Flickr

Removed from 1.7- by A60man, on Flickr

That spare "1.7" Renix you have is NOT for a 1.7 it's for the B200K 360
( carburettor 2 litre from the 240 )

[Clan]

Originally Posted by Two340'sman

Thank you.

I removed the capacitor, no difference.

Next I fitted the Renix unit from the 1.7 340, started the engine and I thought we had cracked it. Engine ran and ticked over nicely, then after a few min same old problem, rough and slow idle.

Looked at the distributor cap (was new about 3 years ago) and it didn't look that good inside, so fitted a new one, again thought we had solved it as initially good tickover, then back to slow and rough tickover. When it changes from good tickover to rough, the exhaust issues a little black smoke that persists until revs are raised.

I'm thinking the temp relation theory is quite likely.

Perhaps tomorrow I'll look for my compression gauge.

you need to determine if the mixture is weak or rich when the problem happens . with the air filter off spray some brake cleaner down the carb , if the revs go up its weak ... then introduce some air into the brake servo line some how when its playing up , if the revs go up its too rich ..

[Laird Scooby]

Originally Posted by Clan

you need to determine if the mixture is weak or rich when the problem happens . with the air filter off spray some brake cleaner down the carb , if the revs go up its weak ... then introduce some air into the brake servo line some how when its playing up , if the revs go up its too rich ..

Brake cleaner no longer works!

All the VOCs have been removed so it's about as flammable as a wet lettuce! Need to ue WD40 as that is STILL a petroleum distillate.

Also, if it's black smoke, it's running rich. I don't know which carb it has, if it's that horrible Solex twin-choke thing then it might have one of those vacuum operated accelerator pumps on it. In common with Webers so equipped, two things can cause this to happen. One is the diaphragm in the carb that the vacuum operates has gone weak and/or has a pinhole or split in it that opens up once warm second likelihood is the small bore vacuum hose, usually only a couple of inches long if that, can have a pibhole or is perished but again, once it gets hot and flexible, allows air in which pushes against the diaphragm causing a discharge from the booster jet.

Not sure when or if they changed from this design or if it ever had it but i've seen many similar engines that have had this problem. Also general wear in the carb can sometimes cause it but isn't quite as common.

[Clan]

Originally Posted by Laird Scooby

Brake cleaner no longer works!

All the VOCs have been removed so it's about as flammable as a wet lettuce! Need to ue WD40 as that is STILL a petroleum distillate.

Also, if it's black smoke, it's running rich. I don't know which carb it has, if it's that horrible Solex twin-choke thing then it might have one of those vacuum operated accelerator pumps on it. In common with Webers so equipped, two things can cause this to happen. One is the diaphragm in the carb that the vacuum operates has gone weak and/or has a pinhole or split in it that opens up once warm second likelihood is the small bore vacuum hose, usually only a couple of inches long if that, can have a pibhole or is perished but again, once it gets hot and flexible, allows air in which pushes against the diaphragm causing a discharge from the booster jet.

Not sure when or if they changed from this design or if it ever had it but i've seen many similar engines that have had this problem. Also general wear in the carb can sometimes cause it but isn't quite as common.

Brake cleaner still works for me ...

The 1.7 has the solex carb ,
The B14 has always had the quality weber twin choke 32 DIR in various improved models over the years , a very good carb. Its not subject to wear at all .

[Two340'sman]

Originally Posted by Clan

That spare "1.7" Renix you have is NOT for a 1.7 it's for the B200K 360
( carburettor 2 litre from the 240 )

lol! was on my 1.7 GLE for the ten years that I had it! Previous owner must have put it on. Car went OK, even got about 55 MPG on a long run.

[Two340'sman]

" Originally Posted by Clan View Post
you need to determine if the mixture is weak or rich when the problem happens . with the air filter off spray some brake cleaner down the carb , if the revs go up its weak ... then introduce some air into the brake servo line some how when its playing up , if the revs go up its too rich .."

I did something like this test, air filter off, rough slow idle, sprayed WD40 into carb and engine revs rise, and idle better.

Confusing thing is black smoke comes out whilst rough slow idling.

[Laird Scooby]

Originally Posted by Two340'sman

" Originally Posted by Clan View Post
you need to determine if the mixture is weak or rich when the problem happens . with the air filter off spray some brake cleaner down the carb , if the revs go up its weak ... then introduce some air into the brake servo line some how when its playing up , if the revs go up its too rich .."

I did something like this test, air filter off, rough slow idle, sprayed WD40 into carb and engine revs rise, and idle better.

Confusing thing is black smoke comes out whilst rough slow idling.

When were the plugs last changed, what did you set the gap to and what brand of plugs did you use?

*** EDIT *** I seem to recall you said you checked/changed the HT leads - did you notice any brown rings on the ceramic insulator on the plugs?

[Two340'sman]

Originally Posted by Laird Scooby

When were the plugs last changed, what did you set the gap to and what brand of plugs did you use?

*** EDIT *** I seem to recall you said you checked/changed the HT leads - did you notice any brown rings on the ceramic insulator on the plugs?

Yes, I did check the plugs, they looked OK, think I made the gap 30 thou".

Yes, new ign leads too.

Cleaned the ceramic insulation.

I could try new plugs.

[Laird Scooby]

Originally Posted by Two340'sman

Yes, I did check the plugs, they looked OK, think I made the gap 30 thou".

Yes, new ign leads too.

Cleaned the ceramic insulation.

I could try new plugs.

Gap is about right (from what i remember of them) but the important bit is what brand plugs are you using?

Also if the insulators have brown rings on, there is "blow-by" past the insulator. Sooner or later this will cause tracking on the outside of the plug and when the pugs get warm, a slight leak so will help to cause a misfire.

I'm thinking if one or two plugs are just slightly misfiring, this will cause the black smoke as it will be unburned fuel in the exhaust that burns once the others fire normally. It will also make the others run slightly richer so again, extra fuel going in.

I would use NGK, Denso or Bosch in that order of preference. Also bear in mind that new plugs are generally (certainly NGK) are set by default to 0.9mm or 0.036" so will need closing up slightly before use.