[T3] Fwd: Engine Backfire

[Dave Hall]

Backfiring may be due to air leaks in the left part of the exhaust system -
not sure how much of the original system would be in place with a trike
though.

I was suspecting fuel leaks from the injector nozzle, not external, which
wouldn't cause a backfire - more likely an engine fire!  You would have to
remove the injector bank and pressurise the fuel ring main to see fuel leaks
from the nozzles.

Dave.
UK VW Type 3&4 Club
===================

-----Original Message-----
From: type3-vwtype3.org-bounces at lists.vwtype3.org
[mailto:type3-vwtype3.org-bounces at lists.vwtype3.org] On Behalf Of
BilDylJ at aol.com
Sent: 18 July 2012 15:40
To: type3 at vwtype3.org
Subject: [T3] Fwd: Engine Backfire


 

 
Thanks Jim
I appreciate the help.
My engine ran good for about 4 yr's. I had to leave it outside (covered} for
about 2 mo. and it wouldn't start after. I had it checked  by
2 { Certified } VW mechanic's they got  it running but it has been
backfiring on the left side 3 & 4 cylinders ever since. They can't  stop it
from backfiring. I thought maybe the rubber rings on one of the  injectors
were leaking air. There are no fuel leaks from the injectors or the  hoses.
The engine starts and run's pretty good But it still starts backfiring every
time you let off on the throttle and hold it at a steady speed. {approx.  
30 mph}
The engine is in a Trike motorcycle and no one wants to mess with  it.
It must have been set up alright originally it ran good for 4 yr's. 

                                   Thanks Again !
 
 Billy D



 
 
In a message dated 7/16/2012 5:40:58 P.M. Eastern Daylight Time,
jadney at vwtype3.org writes:

On 16 Jul  2012 at 16:48, BilDylJ at aol.com wrote:

> Can anyone out there tell  me how to change the fuel injectors on a 
> 1972 type 3  engine.

I would not suspect injector problems as the source of engine backfire,
unless you have some non-Bosch injectors there. Non-Bosch injectors can
usually be easily identified by the fact that they don't have the nicely
rounded corners around the electrical connector.

If you're having problems not related to leaking gas,  I suggest you go to
the bottom of this message and check the tightness  of all 2 push on
electrical connectors.

There is very seldom any  need to replace all 4 injectors, unless you're
talking about an engine  that has not run in decades. If the problem is gas
leaking from failed  original hoses crimped onto the injectors, the crimp
can be cut off and  that short piece of hose replaced. However, you still
have to remove the  injectors to do this.

Removing the injectors is a mid level job,  neither easy nor really hard,
but it is cramped, especially working on  the LHS.

Start on the right. Remove the air cleaner.

Unplug  the electrical connectors from the injectors. Don't pull on the
wires,  pull on the connector body. (You can feel the body thru the rubber
boot.)

Loosen the clamps that attach the multiple port "Tee" to the 2 injectors.

Rock the Tee back and forth while pulling it out of  the injectors. 
When it comes out gas will spill. Do this outside or with  good ventilation.
No smoking.

Find a combination of 10 mm socket  and short extension that will let you
get to the nuts in the center of  the injector mount. Remove both nuts and
washers.

Pull both  injectors outwards, along with the mounting hardware. Each
injector will  have a large and small rubber ring. The small ring may stay
in the  socket when you pull the injector out. The small rings are still
okay as  long as they are plyable and not broken all the way thru. The large
rings are okay as long as they will still fit in the phenolic  retainer.

Note that there should be a small metal sleeve surrounding  each mounting
stud. They may stick inside the phenolic mounting plate.  
They are necessary to keep from breaking the plate.

The phenolic  plate may be broken if the injector has been leaking. If this
is the  case, you will also need to replace that rubber ring, because it
will be  swollen too large to fit back in the plate. I just swap these and
let  the gas slowly evaporate from the rubber and use them again in a few
months.

Installation is the reverse of removal. Repeat on the  LHS.

I have all the parts and I can replace the hose ends on the  injectors if
that's a problem for you.

I have had poor results  with non-Bosch injectors. That's about the only
time I ever replace an  injector. I have new Bosch injectors, too, but I
never recommend  replacing injectors unless there's some good reason to.
They do NOT seem  to wear out, but they sometimes develop leaks that can't
be fixed. Small  thru leaks can be ignored.

If you are having injector problems, you  should also check that the
electrical connectors are tight on the  injectors. Bosch made a major
mistake at some point in their production:  They reduced the thickness of
the material used to make the injector  pins. This causes huge problems with
poor connectons there. To fix this,  you must remove each pin from it's
connector body and very carefully  squeeze it down until it is snug on the
injector pin. Then snap it back  into the connector body. This is actually
more work than removing the injectors.

--
*******************************
Jim Adney,  jadney at vwtype3.org
Madison, Wisconsin,  USA
*******************************

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