SAAB V4 Forum
SAAB V4 Forum
Home | Profile | Register | Active Topics | Members | Search | FAQ
 All Forums
 Technical
 General Technical
 Weak mixture on one bank, Weber 32/36 DGV

Note: You must be registered in order to post a reply.
To register, click here. Registration is FREE!

Screensize:
UserName:
Password:
Format Mode:
Format:BoldItalicizedUnderlineStrikethrough Align LeftCenteredAlign Right Horizontal Rule Insert HyperlinkInsert EmailInsert Image Insert CodeInsert QuoteInsert List
  
Message:

* HTML is OFF
* Forum Code is ON
Smilies
Smile [:)]Big Smile [:D]Cool [8D]Blush [:I]
Tongue [:P]Evil [):]Wink [;)]Clown [:o)]
Black Eye [B)]Eight Ball [8]Frown [:(]Shy [8)]
Shocked [:0]Angry [:(!]Dead [xx(]Sleepy [|)]
Kisses [:X]Approve [^]Disapprove [V]Question [?]

 
Check here to subscribe to this topic.
  

T O P I C    R E V I E W
andydeans3Posted - 07 Aug 2021 : 18:07:25
The carb is a 32/36 Twin choke Weber DGV. Brand new about 6 years ago.

Historically the mixture always seemed correct, nice sandy brown coloured plugs.
Then as part of a fault finding exercise I replaced the mechanical fuel pump, with an electric pump, meant for an MGB.
It was about then I noticed that the plugs were nearly white.
I also refitted the mechanical pump, and now have the electric pump, feeding the mechanical pump.

I have been in touch with Fast Road cars who suggested I up the idle jets from 55/50, to 60/55.
This I have done.
The pair of plugs below are one from the left bank, (white),and one from the right bank, (reasonable sandy brown colour).
The single plug is from the left bank. I didn't take out the front right hand plug because of the hassle with the alternator in the way!
The plug colours you see are AFTER upping the idle jets.

Does anyone have any other ideas? Especially, why is one bank weak, and one bank seem about right.





1978 LHD SAAB 96
1978 MGB Roadster
2008 LHD "Classic" Renault Twingo
1991 Nissan Figaro
15   L A T E S T    R E P L I E S    (Newest First)
rattyPosted - 27 Sep 2021 : 11:29:30
The moral to all this is change the plugs if you have a plug problem, whatever, change them for what it doesn't cost, and compare! I have had occasional problems with NGK's over the years. Still reckon they are the best going for the money.
andydeans3Posted - 22 Sep 2021 : 14:05:34
The 4 plugs are below, numbered 1 to 4, left to right.
I think there's more of a consistency now.
I checked the compression again today, with a different compression tester from before.
130 to 145 psi across all 4.

[url=https://flic.kr/p/2mt9UpL


1978 LHD SAAB 96
1978 MGB Roadster
2008 LHD "Classic" Renault Twingo
1991 Nissan Figaro
andydeans3Posted - 14 Sep 2021 : 19:54:38
quote:
Originally posted by melle
Really difficult to diagnose something like this from a distance, so I can only shoot ideas from the hip really. Does the no. 3 plug seat OK, and is there no damage to the threads or the seat in the head? HG leak, i.e., coolant leak to no. 3 cylinder? How's the coolant level and ave you recently done a compression test? When did you last adjust the valves? Does the thermostat open at all?

Melle
-Not a drop of water lost on this weekend's trip to Buxton, Stratford, Hatton park, and home.

- Compressions checked a few weeks ago. All around the 140 psi mark
- Tappets checked at the same time.
- As far as I'm aware the thermostat opens. I've just done a big journey over the weekend, and had no cooling/heating issues.

What I have done today, is fit new plugs.
I'll report back what they look like next week.

Andy

www.saabv4.com



1978 LHD SAAB 96
1978 MGB Roadster
2008 LHD "Classic" Renault Twingo
1991 Nissan Figaro
mellePosted - 14 Sep 2021 : 07:53:33
Really difficult to diagnose something like this from a distance, so I can only shoot ideas from the hip really. Does the no. 3 plug seat OK, and is there no damage to the threads or the seat in the head? HG leak, i.e., coolant leak to no. 3 cylinder? How's the coolant level and ave you recently done a compression test? When did you last adjust the valves? Does the thermostat open at all?

www.saabv4.com
andydeans3Posted - 14 Sep 2021 : 01:05:42
I'm having a fuel starvation saga, it's across on the UKSAABS site.
I had all the plugs out on Thursday, on my way down to Stratford.

Well, plug number 3 is still white as a ghost......
Any more ideas as to how I can be drawing extra air, into one cylinder only?

1978 LHD SAAB 96
1978 MGB Roadster
2008 LHD "Classic" Renault Twingo
1991 Nissan Figaro
WoodyPosted - 26 Aug 2021 : 15:02:49
The air bleed parts of inlet manifold used to have copper plates in the original Saab gaskets.
mellePosted - 24 Aug 2021 : 16:49:42
The small holes are air bleeds.

www.saabv4.com
andydeans3Posted - 24 Aug 2021 : 13:15:10
I've come back to look at this issue again.
I can confirm that the plugs are NGK BP6ES, bought from Malbrad.

I have now removed the inlet manifold, to change the inlet manifold gasket. I can see no evidence of any air leaks around cylinder number 3, or anywhere else for that matter.

One question I wanted ask the "assembled".
Why are there 2 blocked off waterways at the front of the engine. Just a small pin hole to balance the water pressure I suppose.
You can see them at the left hand end of the photo below. The new gasket. The old gasket is identical. Just morbid curiosity.

The lower photos show the manifold after I removed the old gasket.
It came off quite cleanly, just leaving a bit of residue round the water ports.

Since I found no clear evidence of an air leak, I don't think I've solved this issue...............Perhaps a very, very small air leak, that's left no trace?
We'll see what happens when I get it all back together again, and running.



Before Cleaning up faces


After cleaning up faces



I used a hoover to prevent dust/crud falling into the engine ports, while removing old gasket material.





1978 LHD SAAB 96
1978 MGB Roadster
2008 LHD "Classic" Renault Twingo
1991 Nissan Figaro
SAAB96LPosted - 10 Aug 2021 : 14:13:29
Andy,

Could this be as simple as, a faulty spark plug where its heat range resilience is starting to degrade ??

My experience of spark plugs where the insulator goes white is:

Ignition too far advanced / lean fuel mixture / cooling issue within the combustion chamber chamber which is often caused by excessive combustion deposits.

Spark plug insulators start to go white, when the combustion chamber reaches temperatures in excess of about 850 degrees C for a prolonged period of time. The optimum operating range is between 450 C and 850 C. As you can see, the examples I mentioned earlier will certainly raise the combustion chamber operating temperature.

However, over a period of time I would expect all the plugs to be white if one of the above was applicable - hence my opening line concerning a single defective plug.

If you have a digital laser thermometer, that would certainly be a useful test to ascertain that the plugs and the immediate surrounding area of the cylinder head reads the same within reason.

You didn't confirm if you are using BP6ES plugs and I cannot make that out from the previous photos.

Just a few ideas.

Regards.

Richard.
andydeans3Posted - 10 Aug 2021 : 12:11:13
Here are all 4 plugs, 1 and 2 at the top. 3 and 4 at the bottom.
Number 3 seems much whiter than the other 3.

I have tried spraying WCP all around the inlet manifold, to see if it gives any indication of air being drawn, but that drew a blank.
Same around the carburettor flanges and various connections in the area. Nothing.



1978 LHD SAAB 96
1978 MGB Roadster
2008 LHD "Classic" Renault Twingo
1991 Nissan Figaro
andydeans3Posted - 09 Aug 2021 : 22:40:11
Aye, Melle, the bolts are not slack so changing the gasket was my next port of call.

The gasket in the car now, and the spare inlet manifold gasket that I have, were bought from Malbrad, so I'd hope their good quality.
I'm busy doing other things this week, so hope to get back to it next week.
I'm going to Corbridge (Northumberland), Classic show on Sunday 15th August, so also don't want to start fiddling with the car before the show, anyway.
ps was hoping to see you at SAAB Fest this weekend past.

Andy

1978 LHD SAAB 96
1978 MGB Roadster
2008 LHD "Classic" Renault Twingo
1991 Nissan Figaro
mellePosted - 09 Aug 2021 : 20:36:20
Check if the intake manifold bolts are tight, they have a tendency of coming loose over time. If you/ someone else has used an intake gasket from a cheap set it may be worth replacing it with a better one, some are exceptionally poorly made.

www.saabv4.com
DerekPosted - 09 Aug 2021 : 11:38:49
It is a twin choke but is progressive so the first "economy" choke opens fist and then the second "performance choke opens when you want more go. That way the gas speed in the first choke can be high fo efficiency.

Model Number Common Name Notes
32/36 DGV (5A) DGV Progressive throttles, Manual choke
(standard for Formula Ford 1600, Formula Ford 2000, and Sports 2000)
32/36 DGAV DGV Automatic choke (A = Aqua; water-operated)
32/36 DGEV DGV Automatic choke (E = Electrically-operated)
32/36 DFAV, 32/36 DFEV DFV Should be a mirror-image of DGV series,
but only the jets interchange!*
38/38 DGAS, 38/38 DGES DGAS Synchronous throttles, otherwise a DGV

40 DCOE, 45 DCOE, 48 DCO, 50 DCO, 55 DCOE DCOE Dual-throat side draft. E used to indicate a trapezoidal mount. The E has largely been dropped but the trapezoid remains.
46 IDA, 48 IDA IDA (dual) Dual-throat downdraft
40 IDA 3, 46 IDA 3 IDA (triple) 3-throat downdraft specifically for Porsche flat-6
(nothing interchanges with IDA dual!)
40 IDF, 44 IDF IDF Dual-throat downdraft
andydeans3Posted - 08 Aug 2021 : 21:36:44
Derek
I wasn't aware of the strict twin choke definition.
Always thought of it as a twin choke carb.
Anyway.....
I use a ring spanner to get that number 1 plug out, it's just a hassle.
I will take it out the morn.
I've checked around the carb to manifold connections with WD 40, perhaps need to move down to the inlet manifold gasket.
I'm thinking the inlet manifold perhaps needs to come off, I've got a new gasket.....

1978 LHD SAAB 96
1978 MGB Roadster
2008 LHD "Classic" Renault Twingo
1991 Nissan Figaro
DerekPosted - 08 Aug 2021 : 17:34:38
The 32/36 isn't a dual choke carb as both the 32 and the 36 feed all cylinders. That means that any given throttle opening the mixture is feeding the manifold. You could have an air leak on that side (manifold to head gasket, check manifold nuts/bolts) if the weak plugs are both from the same head. From your post that seems to be the case but I'd persevere and get the awkward plug out. Your Saab tool kit appears to be missing the short spanner with the stubby lever welded to it? I think it's also possible to have an exhaust leak cause this condition?

Snitz Forums 2000
SAAB V4 Forum© 2000-04 Snitz CommunicationsGo To Top Of Page