'87 760 (B230FT) Injector Test

I have a no start problem that I believe is a fuel issue. I have
checked everything up to the injector rail and I need some help with
diagnosis. I could hear nothing with the screwdriver to the injector
clicking noise test while the engine was being cranked. I checked the
resistance on the injectors and they are all reading 2.7 ohms.
According to Chilton etc they should read 16 ohms but I have a hard
time believing all four injectors died at once. I confirmed a
connection between the fuel rail grounds and battery "-". I can smell a
little gas at the fuel pressure regulator vacuum hose but I have not
read anything that indicated this could cause a complete no start
problem.
Thanks in advance for any help.

 

I am understanding you have determined you have good pressure at the rail.
Have you checked for spark? If that is missing, the Hall sensor may have
died... without the signal from that, the injectors never fire.

I suspect the 16 ohm reading includes the ballast resistors or is for the
non-turbo injectors. My B230FT injectors measure about 2.5 ohms. With just
one injector disconnected I read about 5 ohms to ground on one side of the
connector and about 7 ohms to ground on the other side.

Mike

 

On an YM87 2.7 Ohms is correct for blue top injectors (aluminum low
resistance quick acting). If you were to measure the resisitance between
the injector wire pairs at the control unit you would see ~4 Ohms since
the resistance from the resistor pack in the turbo harness would be
added in. If you get no flash from the power wire to the injector while
cranking then either the computer has died, the harness is bad or there
is no spark. If you have fuel pressure at the rail and the fuel pump
runs while cranking then you have spark.

Bob

 

Thanks for the responses.

I have verified there is fuel in the rail. I believe there is spark
because starter fluid in the air intake will cause the engine to start
for an instant. I think the problem is that the injectors are not
getting a pulse. I determined this by plugging a voltmeter into the
back of an injector plug and watching for any sign of voltage when I
crank the engine. here was none. Does this test make sense?

I have already checked what I could on the ECU using the Chilton
information and according to the guidelines the system grounds, air mas
meter and coolant temp sensor are okay. The throttle switch test failed
at the full throttle position but passed at the idle position. I also
checked the air mass meter at the meter itself. There was no mention of
a check for injector control on the ECU.

 

Look for the injector resistor pack, it's on the inner fender near the
front of the car. Verify no broken wires and clean the connections.
Believe it or not, this part does not use waterproof terminals.

Also look for a black relay with 4 round pins on or near one of the
shock towers. This relay supplies power to the injectors.

--
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.)

 

Thanks again for the help.

I believe I ohmed out the resistor pack a while back and it was okay
but I will check it again. Is the black relay you are referring to the
radio suppression relay? I encountered some confusion regarding this
earlier. I have a black relay on the driver's side near the shock tower
but I came to the conclusion after some research this is not a
"feature" on the '87 turbos. Do you agree?

If not, the literature I encountered indicated that I should swap this
with the electric fan relay but I could not find a second relay. Do you
have any idea where I should look for the identical fan relay?

Some the diagrams I have seen include inline fuses for the injection
system that are under the hood. I have not seens any references to
these in trouble shooting tips so I have avoiding them. Any chance they
could be the problem?

 

YM87 only had the radio suppression (injector) relay under the hood by
the PS reservoir bottle. The cooling fan relay was a five pin type in
the central electrical panel behind the ashtray.

Bob

 

Right. And the suppression relay was something they added part way
through the year, and as an free update (recall?) to ones (and 85 and 86
model years) that had already been sold. This is why it may not show in
all literature and manuals.

This poorly named relay is called (by Volvo) the radio suppression
relay. What is does is supply power directly from the battery to
components that require pulsing (on-off) power - like the injectors.
This isolates this "noise" from the supply to the radio, thus
"suppressing" interference.

--
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.)

 

This is great info. Things are starting to make sense.
I only have the relay by the driver side shock tower but it has the
correct part number so unless there is another use for that relay I
will assume it could be the culprit.
Any suggestions on testing or should I just replace it?
Any ideas on where I could find one?

 

That relay sends power to the resistor pack. There's one wire at the
resistor pack that is connected to all 4 resistors. The other 4 wires
go to the injectors. The other wires at the injectors are grounded by
the FI computer, which is what opens the fuel path. Check for power at
the resistor pack.

--
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 problem was the wire that inputs the voltage to the resistor pack
was broken inside the plastic resistor pack connector. I found it when
I went to clip a volt meter to the line to see if anything was coming
out of the radio suppression relay.
I picked up two spare resistor packs in good shape and a couple relays
just in case at a salvage yard for $21. Replaced the resistor pack and
used my original relay and it started right up.

Thanks for the all the help.