38DGAS air/vacuum pipes

Discuss and exchange views and technical information about our cars.

Moderators: scimjim, philhoward, Lukeyboy46, erikscimitardemon, Roger Pennington

Post Reply
Wasman
RSSOC Member
Posts: 112
Joined: Sun Nov 23, 2014 11:36 pm

38DGAS air/vacuum pipes

Post by Wasman » Sat Mar 23, 2019 4:28 pm

Right I've done my bit and searched the forum, can't see any evidence of this being discussed in any detail.

I'm chasing a misfire and I noticed a definite pause in the engine when I touch a small pipe on the carb. It's a new 38DGAS from AJL.

My questions:

First:
What does the short pipe connecting the base of the carb on the LHS to what looks like a casting holding a diaphram do? I've seen it in other pictures, but what is it's purpose? Could it safely be removed and if so should the pipes be blocked or left open??
IMG_20190323_162438.jpg
The short pipe
IMG_20190323_162438.jpg (191.41 KiB) Viewed 908 times
Second:
What should be on the end of a brass pipe on the RHS of the carb? Mine is open, should it be blocked??
IMG_20190323_162504.jpg
The brass pipe
IMG_20190323_162504.jpg (161.83 KiB) Viewed 908 times
All 'sides' are from the perspective of the driver.

Thanks in advance!



User avatar
scimjim
RSSOC Member
Posts: 37439
Joined: Sun Oct 01, 2006 10:08 pm
Location: Gloucester
Has thanked: 130 times
Been thanked: 948 times

38DGAS air/vacuum pipes

Post by scimjim » Sat Mar 23, 2019 4:40 pm

First one is the acceleration valve (squirts fuel in when you floor it to prevent the hesitation caused by a delay in the fuel from the main jets responding).

Second one goes to the standard air filter - I tend to block any unused pipes.


Jim King

SECURE DRY STORAGE FOR YOUR SCIMITAR

Current: SE5 (8Ball), TI SS1 (snotty), 1600 SS1 (G97), 1600 SS1 (C686CCR), 2.5TD SE5a (diesel 5a), 6 x random other SS1s.
Previous: SE5, 3 x SE5a, 2 x SE6a, 3 x SE6b, GTC, 2.9i GTC, 3 x 1600 SS1, 1300 SS1, Mk1 Ti Sabre, Mk1.5 CVH Sabre
Chief mechanic for: 1400 K series SS1 (Megan3), 1400 CVH EFi SS1 (Grawpy), 1300 SS1 (Number One) & Sarah's coupe.
CURE THE FAULT - NOT THE SYMPTOMS

User avatar
MadMax
Posts: 136
Joined: Thu Aug 27, 2015 10:25 am
Has thanked: 2 times
Been thanked: 2 times

38DGAS air/vacuum pipes

Post by MadMax » Sat Mar 23, 2019 4:53 pm

I thought the accelerator pump was on the RH side of the carb and has a mechenical linkage? (seen in pic 2)

The stub showing is plumbed into my vac advance on the dizzy.


Max Benton
Reading, Berks
'A HOT N' - Gold 1600 Small Sports
'Zeus' - Yellow SE5a

Wasman
RSSOC Member
Posts: 112
Joined: Sun Nov 23, 2014 11:36 pm

38DGAS air/vacuum pipes

Post by Wasman » Sat Mar 23, 2019 4:55 pm

Thanks guys. I doubt that's my problem as the car is undriveable at the moment, the misfire has got much worse recently. But that's for another post rather than go off topic!



User avatar
AJL Electronics
RSSOC Member
Posts: 7747
Joined: Fri Oct 17, 2008 8:49 pm
Location: Gloucester
Has thanked: 44 times
Been thanked: 231 times
Contact:

38DGAS air/vacuum pipes

Post by AJL Electronics » Sat Mar 23, 2019 5:05 pm

Give me a ring Monday if you are still having difficulty.

There are two vacuum ports. The one on the side of the carburettor is for the vacuum advance to the distributor. If not connected it will cause a weak mixture. The one at the back between the quadrants is for the air cleaner motor. If not being used, it MUST be blanked off, the air leak from notmdoing so will make it very hard to keep running.


Yes, we can mend your Scimitar!
Order your Scimitar parts any hour of the day at http://www.classicmicrocars.com (member's discounts).

Fancy a holiday in Gael, France? http://www.ianrhu.com

There is no point trying to teach a pig to sing. It doesn't work and it annoys the pig.

User avatar
scimjim
RSSOC Member
Posts: 37439
Joined: Sun Oct 01, 2006 10:08 pm
Location: Gloucester
Has thanked: 130 times
Been thanked: 948 times

38DGAS air/vacuum pipes

Post by scimjim » Sat Mar 23, 2019 5:26 pm

MadMax wrote:
Sat Mar 23, 2019 4:53 pm
I thought the accelerator pump was on the RH side of the carb and has a mechenical linkage? (seen in pic 2)

The stub showing is plumbed into my vac advance on the dizzy.
You’re right - the other side is the anti-stall valve.


Jim King

SECURE DRY STORAGE FOR YOUR SCIMITAR

Current: SE5 (8Ball), TI SS1 (snotty), 1600 SS1 (G97), 1600 SS1 (C686CCR), 2.5TD SE5a (diesel 5a), 6 x random other SS1s.
Previous: SE5, 3 x SE5a, 2 x SE6a, 3 x SE6b, GTC, 2.9i GTC, 3 x 1600 SS1, 1300 SS1, Mk1 Ti Sabre, Mk1.5 CVH Sabre
Chief mechanic for: 1400 K series SS1 (Megan3), 1400 CVH EFi SS1 (Grawpy), 1300 SS1 (Number One) & Sarah's coupe.
CURE THE FAULT - NOT THE SYMPTOMS

Wasman
RSSOC Member
Posts: 112
Joined: Sun Nov 23, 2014 11:36 pm

38DGAS air/vacuum pipes

Post by Wasman » Sun Mar 24, 2019 8:45 pm

Thanks for all the useful knowledge guys and offer for phone support from AJL, as usual spot on. Thanks especially to Martin who came round with a spare carb, dizzy and other bits, spent his Sunday afternoon helping nail down the cause of a long running problem! (Carb related but with ignition symptoms!!).



Post Reply

Return to “General Technical Discussion”