J Sweet: which component to check?

Re: 92 740 wagon B230 turbo LH Jetronic....

Ok...I finally ran my own tests today. Spark is strong to all 4
cylinders. Fuel pressure in the rail is 42 when cranking. I lifted the
entire fuel rail/injectors up and watched them while cranking. They
are not leaking fuel. When cranked they are spraying a LOT of fuel, I
think it is way too much, from the first shot on. It remains the same
large volume no matter how long you crank. So I figured out what is
happening. On the first attempt to start car, it "fires" like it is
going to start for about one second, then nothing--- because the
cylinders are being flooded with gas. This is why it will not fire
again at all unless the car sits for a day.
Whatever it is, it was making the car run rich for a couple of
months or so. Ocasionally during this time, the defect would get
suddenly worse, and the injectors would go to max, flooding the
engine...causing it to die while driving. I have a strong supspicion
it is a bad or missing sensor input, probably not the ECM itself that
is causing this. But....the ECM is not setting any codes to show what
fuel control component is bad.
THe crummy 82-88 740 Haynes manual I have says there are six inputs
to the ECM that control fuel delivery/mixture: AMM, ECT, 02 sensor,
plus an air control valve and transmission and charge overpressure
switch.

Problem is, I don't have specific info on how to test these
components. Is there perhaps one component that, if bad, would make
the injectors go full rich on cranking?


I think that when a car *runs* rich, most likely thing is a bad O2
sensor...but doesn't the control system ignore the O2 sensor until the
engine is up to operating temp? That would mean that it is not the
culprit in this case.

Thanks, Geronimo

 

[ ... ]

Try disconnecting each sensor, one at a time, and see if one changes
the behavior to limp-home mode.

While you're at it, clean the contacts on each and make sure they're
making a good connection.


Gary

 

Can't observe any change to limp-home mode when the car won't even
start.
Geronimo

 

After what I went through with my '90 240, when people start a
sentence with, "it was running OK, but then it..." I interrupt with
"AMM." It drove me crazy when mine failed. I spent a week testing
everything I could with an ohm meter and such according to Bentley.
Since I live a good 25 miles from anywhere that could work on it or
even just test it, I had to troubleshot it myself- it wasn't running
well enough to drive anywhere safely. It would post a bad AMM code
SOMETIMES but not all the time. If you can find a pick and pull yard,
pick one up and switch it. Worst case is then you would have a spare,
or one to sell on eBay. I bought 3 at the local yard- one to replace
the bad one, then I picked up two more- one is in the car as a spare
and one for the box of parts in the garage- you NEVER know... ;-)

__ __
Randy & \ \/ /alerie's
\__/olvos
'90 245 Estate - '93 965 Estate
"Shelby" & "Kate"

 

Well, I have another AMM which I kept when my 89 Volvo 740 non-turbo
sedan died. It looks physically identical to the one in the wagon.
There are two rows of numbers, the upper shorter number is different,
but the very long number below is identical. So I am not sure if I can
use this one inthe wagon--- 92 740 *turbo*. It might have different
air flow from the sedan, since it is a turbo intake. Could kick
myself for not removing the ECU from the sedan also!
The other thing that will prevent it from starting is a bad crank
pos. sensor, It is a new one, but still could have failed, so I guess
I will check taht. Chilton says it is supposed to be between 200-500
ohms if good. Don't have a clue whether it could make the mixture way
to rich , though.

Also I need to know for sure which one of abt four emisson
control/ECU systems the wagon has. I think it is LH Jetronic.... do I
need to look on the ECU itself to verify? The other thing is that I
got this CHilton manual today, and it shows the LH jetronic as having
a SEPARATE fuel control module....although no parts dealers are
listing a fuel control computer available for this car. Then
elsewehere in the same manual it says that it is the ECU that sends
the signals to the injectors.

Thanks Geronimo

 

What are the numbers?

I wouldn't trust ohm readings on sensors other than those for
temperature, and I certainly wouldn't trust Chiltons. I doubt a crank
sensor would make it go full rich.

Have you tried connecting a 12V bulb to an injector plug and see if it
glows with the key on but the engine not cranking?

 

Since you don't say where you are, I'll assume you're in the US.
Air mass meters are compatible for both turbos and non turbos with
LH2.4. Non turbos started in 1989 model year (both 8 and 16 valve),
turbos didn't get LH2.4 until 1990 model year. Exceptions are 8 valve
non turbo 740s and 940s with Regina fuel systems (no air mass meter) and
some later manual transmission 240s with LH3.1, which has a thin film
type air mass meter, (looks completely different inside) as opposed to
the hot wire type on LH2.4.

So it sounds like your air mass meters are interchangeable.

--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

The injector rail is pulled up. I put a noid light on each injector,
and it does not flash until cranked, and none of the injectors are
leaking---they are all closed as they should be until cranked. I
think they are spraying way to much fuel from the first pulse. SO that
is why I am concentrating on some sensor component in control system.

I got a Chilton as that was what was available from local store, I
hear there is some Bentley manual, probably a lot better (don't know
where to get) and I have the link to site with the actual electrical
diagram----but pricey at $40.

 

And you're sure it has a spark? Fuel flow with no spark will cause wet
plugs as well.

 

Well, I got one of those adjustable spark-gap testers that has ground
clip, and checked each spark wire. Each one has a spark with it set to
20mm. I know it is a long shot, but would it be possible that the
spark tests OK with the tester, but I am losing spark under
compression, in actual operation? The only way I can think of to test
whether they are still actually firing under compression would be to
read current through the high-tension lead from the coil....but I have
no gadget to do that. If there is voltage, but no current flow, then
they have stopped firing. Plugs are new/clean.
The distributor cap and rotor are new, but it has an old coil.
It wouldn't be a bad idea to just replace it, since it is old....can I
install a better quality high-output one than OEM? recommendation?

 

Try searching the archives
http://groups.google.com/group/alt.autos.volvo/topics
for the following threads of a year and a half ago from my problem and
solution:
- save me from running around....
- still having problems with my 240
- Still trying to get it running right
- AMM - more Q's
- It's RUNNING!
See if any of that rings a bell or three...
__ __
Randy & \ \/ /alerie's
\__/olvos
'90 245 Estate - '93 965 Estate
"Shelby" & "Kate"

 

Before trying my spare AMM from my defunct 89 non-turbo 740, please
confirm whether its compatible or not. there are three rows of
numbers. The top numbers are different, but the lower two numbers are
exactly the same. here is number on the 92 turbo wagon AMM:

489 30 1A
0280212016
3517020


here is number of the 89 volvo AMM:

281 10 1A
0280212016
3517020

Can I assume if the top numbers don't match it's not compatible and
might fry the computer?


No code such as 1-2-1 is being set for bad AMM.


Thanks Geronimo

 

The other thing I need to know urgently, while fuel rail is
pulled up, is how much gas should an injector pump out when cranked
for, say 30 seconds, for normal operation? If I knew, this I could
verify whether the fuel controls are screwed up, putting out way too
much gas like I am thinking.