[xj] Hard Start / Black smoke ---- Fixed

Hi everyone.

Several weeks back I posted about a hard starting problem I was having with
Goldie, the Desert VdP. Since I finally fixed it, I thought I’d post the
fix for future use.

In the beginning, I was suffering from a hard to start /very rough idle and
clouds (sometimes) of black exhaust - all pretty good indicators of a
fueling problem.

Advice from the group strongly suggested doing a fuel pressure test. So,
boxes were unpacked, tools and gadgets assembled, and a fuel pressure test
was done using a second hose on the cold start injector stub. 3 Tests were
run; the f/p ranged in the 34-37 range, which was within range, given the
old gauge I was using.

This symptom can also indicate an AFM problem, the one that requires the
50-100 mfd capacitor across AFM leads 5-7. This was done, and the problem
was solved… well, went away for a bit.

Last weekend, quite suddenly, I again experienced hard starting, rough
initial idling, and clouds of black smoke. To start, it was necessary to
floor the throttle when cranking, and gingerly apply balanced pressure to
get it running (usually 1500 - 2000 rpm). This was necessary for 5-10
seconds after start, and then all seemed back to normal… Almost. In
traffic standstill, the idle roughness / black smoke returned, and again
either speed or constant rev’ing was needed.

Last night I again tried the F/p check, again in the 34-36 lb range. Had
to head inside for a computer issue, and when I returned, the F/p was down
around 8-10 lbs. Aha. Primed the fuel rail using the
shifter-in-reverse technique, and again, 10 minutes later, was down a bit
below 20lbs. And starting was a bitch.

Reprimed the fuel rail, clamping off the fuel line in and out. 45 minutes
later, it was down at 10lbs. Closer still.

There was no evidence of external leakage from any injector or fuel line.
So, it was to do with one of the 7 injectors.
Let it sit overnight.

This morning, after the overnight cool down, I got the tools and gadgets
necessary to pull and check injectors. The cold start injector was the
easiest, and that’s the one I pulled first. Primed fuel rail pressure using
method above, and… Eureka! At full rail pressure, there was a drop of gas
leaking out of the CSI about every 1.5 to 2 seconds. Clamped the line,
removed the CSI and blew into it. Blew through it is more accurate, as a
stream of gas came out. Put h2o in it, used pressure hose, and out it
sprayed. Got 'im!!!

Had an old CSI in the bit bucket, so I put that in, primed the line. F/P
held at about 32, and no leakage. Mounted same.

The initial start was similar to the problems of before - still a fair
amount of residual gas, but after idle stabilized, I left it for 4 hours and
tried it again on a (desert) cool engine. 4 seconds later it was purring.

So, that’s the verbose story; the short one is don’t rule out leaking
injectors as a cause of hard starting /rich starting /initial black smoke.

Thanks to the ‘helpers’ who provided info, guidance and support

Ken
Maricopa, Sonoran Desert, AZ
87 SIII VdP
134,000 miles,
Pace… Space… Grace… and a smooth idle===================================================
The archives and FAQ will answer many queries on the XJ series…
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Good work Ken! Persistence is the main tool in the box for Jag owners. A few
cans of beer in the frig help too.
;]
Since the injector sticks open, if its coil is ok, why not try the acetone-in-
the-ultrasonic-cleaner trick to see if you can clean it out? Conservation of
spares, you know!–
Alex
79xj6L SII (BRG + wires)
86xj6 SIII (Black)
61 Sprite MkII (Red)
Menlo Park, Calif.

Ken Davis wrote:

Hi everyone.

Several weeks back I posted about a hard starting problem I was having
with Goldie, the Desert VdP. Since I finally fixed it, I thought I’d
post the fix for future use.

[clip]
At full rail pressure, there was a

drop of gas leaking out of the CSI about every 1.5 to 2 seconds.
Clamped the line, removed the CSI and blew into it. Blew through it is
more accurate, as a stream of gas came out. Put h2o in it, used
pressure hose, and out it sprayed. Got 'im!!!

===================================================
The archives and FAQ will answer many queries on the XJ series…
FAQs: http://www.jag-lovers.org/xjlovers/xjfaq/index.html
Archives: http://www.jag-lovers.org/lists/search.html

To remove yourself from this list, go to http://www.jag-lovers.org/cgi-bin/majordomo.

// please trim quoted text to context only

Ken Davis wrote:

Hi everyone.

Several weeks back I posted about a hard starting problem I was having
with Goldie, the Desert VdP. Since I finally fixed it, I thought I’d
post the fix for future use.

In the beginning, I was suffering from a hard to start /very rough
idle and clouds (sometimes) of black exhaust - all pretty good
indicators of a fueling problem.
Last night I again tried the F/p check, again in the 34-36 lb range.
Had to head inside for a computer issue, and when I returned, the F/p
was down around 8-10 lbs. Aha. Primed the fuel rail using the
shifter-in-reverse technique, and again, 10 minutes later, was down a
bit below 20lbs. And starting was a bitch.

Reprimed the fuel rail, clamping off the fuel line in and out. 45
minutes later, it was down at 10lbs. Closer still.

There was no evidence of external leakage from any injector or fuel
line. So, it was to do with one of the 7 injectors.
Let it sit overnight.

This morning, after the overnight cool down, I got the tools and
gadgets necessary to pull and check injectors. The cold start
injector was the easiest, and that’s the one I pulled first. Primed
fuel rail pressure using method above, and… Eureka! At full rail
pressure, there was a drop of gas leaking out of the CSI about every
1.5 to 2 seconds. Clamped the line, removed the CSI and blew into
it. Blew through it is more accurate, as a stream of gas came out.
Put h2o in it, used pressure hose, and out it sprayed. Got 'im!!!

Had an old CSI in the bit bucket, so I put that in, primed the line.
F/P held at about 32, and no leakage. Mounted same.

The initial start was similar to the problems of before - still a fair
amount of residual gas, but after idle stabilized, I left it for 4
hours and tried it again on a (desert) cool engine. 4 seconds later
it was purring.

So, that’s the verbose story; the short one is don’t rule out leaking
injectors as a cause of hard starting /rich starting /initial black
smoke.

Certainly right, Ken - and work well done…

And very good of you to report back. Giving a 20/20 hindsight post fact
analysis I would sure enhance the value of the pressure leakdown test.
Any leak will depressurize the rail very quickly, as little fuel volume
is stored and involved. ‘Normally’ leakdown is the non-return valve
failing - which can be isolated by clamping the rail inlet fuel hose.
But it will cause very little starting troubls anyway…

Clamping can be used for any of the hoses to check for internal leaks,
though since we normally use the CSI tap of for the fuel pressure test
clamping not all encompassing…:slight_smile:

But; if the CSI is suspected; the only way to positively eliminate it
from interfering is to clamp its fuel hose. There is no other way to
ensure that it is passive…:slight_smile:

Frank
xj6 85 Sov Europe (UK/NZ)===================================================
The archives and FAQ will answer many queries on the XJ series…
FAQs: http://www.jag-lovers.org/xjlovers/xjfaq/index.html
Archives: http://www.jag-lovers.org/lists/search.html

To remove yourself from this list, go to http://www.jag-lovers.org/cgi-bin/majordomo.

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