'92 740 died while idling....

It is the 740 turbo model. It has had an intmt problem with no start
(but cranks fine) for a long while, over a year. Come back to it an
hour later, starts right up usually. THis time, whatever it is, I
think has gone out again and is staying bad.....so now it can be
troubleshot. I checked for spark with my inductive spark
tester....there is spark votage still going to the plugs. I thought
it might be the fuel pump relay. So I rigged up a bypass hotwire
direct to the main fuel pump. With the ign on, I can plainly hear
something from the rear of the car running...I guess there is a
tank-mounted pump also? When you stop cranking the car, I can plainly
hear the main pump, the one almost beneath the drivers' seat, running.
Then it stops....until you crank again. I took the line loose off
the fuel pressure regulator return and fuel came gushing out of it
when the car was cranked. So I don't think there is a problem with
fuel delivery. I had to check it there rather than at the fuel rail,
as I can't get the inlet hose connection (to the fuel rail) apart. SO
next I put my noid light (Bosch) tester on each injector. They all
flash. But what is the voltage suppose to be? The bulb only glows
orange, so there couldn't be more than 2 or 3 volts. Maybe the ECU is
pulsing them, but there is a voltage drop, so they are really not
opening. The wife said it just died when she was idling, it never
overheated or made any strange noise. Also, the timeing hasn't really
been checked, but I think when a cr jumps timeing it is when you are
starting it up. The upper cover is off, so I can see that the
pulleys/timing belt seem fine, normal belt tension.


Since it appears spark voltage is still OK, it has to be inadequate
fuel pressure, or injectors not opening, or timing....right?

 

On the turbo, the injectors are wired in series with a resistor pack, so
they only get a couple of volts.
So you have spark and fuel and the engine doesn't run. Well, the only
other thing you need is compression. Is it possible the timing belt is
broken?

--
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.)

 

I'd be double sure about the fuel pumps, filters and clogged lines. The
relay is $20 from FCP Groton, so that should be regular maintenance.
Distributor, rotor, plugs and wires OK?

Maybe just a bad fuel filter.

 

I checked the codes for fuel and igintion, there is none for ign, and
it is giving a code for a bad 02 sensor on F.I. test. (it was turning
on the check engine light for the first minute of operation each time
driven lately). But I think that this would not cause a no start
condition. I checked the timing (just running it through with a
socket on the pulley bolt with upper timing cover off). At zero on the
crankshaft, the mark on the camshaft pulley is about an inch off
alignment with the mark on the back of the timing belt housing! This
is like four or five teeth off....is this what is keeping it from
running? It still feels like there is compression when I turn the
crankshaft pulley (spark plugs have not been removed).

Geronimo

 

I put a tee in for my fuel gauge on the hose that connects direct to
fuel rail, there is 45psi while cranking. With ign on, there is
somewhat less pressure, I guess from the tank pump. So it has plenty
of fuel press. at the rail. I moved the camshaft pulley over abt four
teeth to line up the marks, but still does not start. I took off
each spark wire and connected up a spare spark plug...all four plugs
are getting spark voltage! What else is left? Clogged injectors? But
all four would not clog at the same instant. THe car cranks at
good speed...the batt is charged up...yet the engine does not even try
to fire...it is like the ignition is completely dead....but is not.

I guess I will have to take out no 1 spark plug and check TDC.... it
is possible that I set it to the mark at camshaft, but it could now be
180 deg. out.
As found, there was enough tension on the timing belt so that on the
long open span of it on the right, I could deflect it 1/2 in. in the
middle, pushing real hard.

Seems like the only two possibilities....either I set the cam marks
with piston on exhaust stroke, or all injectors are clogged up.

Ideas?

 

Disconnect the fuel return line at the regulator on the fuel rail and
hold a jar under the regulator. Have someone crank the engine, if the
fuel pump is pumping then fuel will shoot out. I had a pump fail in a
way that it ran but didn't pump so it can happen even if uncommon.

You could also try disconnecting the air mass meter and see if it starts.

 

Hmm ok, so the pump is running, you could pull the fuel rail with the
injectors attached and try cranking to see if they spray fuel.

'92 is new enough that the wiring harness should be fine.