"duh" <nope@notme.com> wrote in message
news:4643d18c$0$27174$742ec2ed@news.sonic.net...
> Ok, I posted the other day about this. Someone said it could be the air
> mass sensor, or the coolant temp monitor.
>
> It just got harder and harder to start.
>
> Here's the history again:
>
> This car has been leaking about 1qt of oil per month for a couple of years
> , and I ran low on oil several times, and there's likely lots of gunk in
> the engine. Not sure what this would do to the fuel system though.
>
> Then, one day, it just started hemmoraging oil. I took it to my regular
> shop, and they said the flame guard was clogged, and it blew out my seals,
> and something on the side of the engine. Luckily I was near the shop at
> the time.
>
> They fixed that, but it was still leaking oil as usual, I took it back,
> and they finally got the damned seals in right, because the leaking pretty
> much stopped.
>
> However, right after that, it began having problems starting.
>
> I finally took it into a shop near where I live now, they replaced the
> distributor cap and rotor, said they were shot. That gave them some spark
> and they were able to start it, but by the time I got there and tried to
> start it, it would almost catch, then die, then wouldn't start. They
> started it by spraying carburator cleaner into a line on the top of the
> engine.
>
> I brought it back in, and they did some more work on it, cleaned the
> coolant sensor, cleaned a bunch of crud out of the ?mixing chamber?, and
> it was working better for a while. Now its getting worse. I've been
> relying on the carburator cleaner to get me started, but its just getting
> worse, running rougher, etc.
>
> They tested the pressure on the fuel pump, and said it was only getting
> about 30psi, where normal was above 40, but they didn't feel this was the
> ultimate problem and didn't want me to throw more money at it in case it
> didn't work. They checked the fuel pump relay and that was ok.
>
> I'm wondering if it might be something as simple as a bunch of crud in my
> gas tank.
>
> I bought some fuel system cleaner, but am leery of using it in case I'm
> going to make something still worse.
>
> The shop who just worked on it said they don't know what else to do and
> the next stop should be a dealer. My experience with dealers is that I
> will be screwed to the wall, but I can't find any reviews for any of the
> independent Volvo mechanics in my area (Fremont/Newark, Ca.)
>
> Any further advice on this would be appreciated.
>
I'm more concerned about the low fuel pressure than the shop is. The fuel
injection system is basically a reckoning system (fine tuned by the O2
sensor when that warms up) that opens the injectors for an amount of time
based on the air consumption reported by the air mass sensor and assuming
the proper fuel pressure. Too low a fuel pressure means too little fuel
injected.

Might as well go ahead with the cleaner. If there is grunge in the system
you'll be better off with it dissolved off the sensitive surfaces. I don't
think the pump is bad - low pressure isn't its style. I'd focus more on the
fuel filter and possibly on the fuel pressure regulator. Any competent
mechanic can change the fuel filter; unless things changed between my '85
and your '91 it is under the car below the driver's seat. It isn't hard to
change with the car on a lift but it is a pain to do with just a creeper.
However, I dunno about the pressure being low. At least in the older 740s
normal pressure is 36 psi, 43 for a turbo.

You can also try the procedure for starting that is used when the check
valve is leaking (allowing fuel pressure in the rail to bleed off when the
engine isn't running.) To do that, hit the starter for half a second or so,
then let the key spring back to the "run" position. Leave it like that about
two seconds while the fuel pump brings the fuel rail up to pressure and try
starting.

Mike

"duh" <nope@notme.com> wrote in message
news:46448f39$0$27200$742ec2ed@news.sonic.net...
> Michael Pardee wrote:
>> "duh" <nope@notme.com> wrote in message
>> news:4643d18c$0$27174$742ec2ed@news.sonic.net...
>>> Ok, I posted the other day about this. Someone said it could be the air
>>> mass sensor, or the coolant temp monitor.
>>>
>>> It just got harder and harder to start.
>>>
>>> Here's the history again:
>>>
>>> This car has been leaking about 1qt of oil per month for a couple of
>>> years , and I ran low on oil several times, and there's likely lots of
>>> gunk in the engine. Not sure what this would do to the fuel system
>>> though.
>>>
>>> Then, one day, it just started hemmoraging oil. I took it to my regular
>>> shop, and they said the flame guard was clogged, and it blew out my
>>> seals, and something on the side of the engine. Luckily I was near the
>>> shop at the time.
>>>
>>> They fixed that, but it was still leaking oil as usual, I took it back,
>>> and they finally got the damned seals in right, because the leaking
>>> pretty much stopped.
>>>
>>> However, right after that, it began having problems starting.
>>>
>>> I finally took it into a shop near where I live now, they replaced the
>>> distributor cap and rotor, said they were shot. That gave them some
>>> spark and they were able to start it, but by the time I got there and
>>> tried to start it, it would almost catch, then die, then wouldn't start.
>>> They started it by spraying carburator cleaner into a line on the top of
>>> the engine.
>>>
>>> I brought it back in, and they did some more work on it, cleaned the
>>> coolant sensor, cleaned a bunch of crud out of the ?mixing chamber?, and
>>> it was working better for a while. Now its getting worse. I've been
>>> relying on the carburator cleaner to get me started, but its just
>>> getting worse, running rougher, etc.
>>>
>>> They tested the pressure on the fuel pump, and said it was only getting
>>> about 30psi, where normal was above 40, but they didn't feel this was
>>> the ultimate problem and didn't want me to throw more money at it in
>>> case it didn't work. They checked the fuel pump relay and that was ok.
>>>
>>> I'm wondering if it might be something as simple as a bunch of crud in
>>> my gas tank.
>>>
>>> I bought some fuel system cleaner, but am leery of using it in case I'm
>>> going to make something still worse.
>>>
>>> The shop who just worked on it said they don't know what else to do and
>>> the next stop should be a dealer. My experience with dealers is that I
>>> will be screwed to the wall, but I can't find any reviews for any of the
>>> independent Volvo mechanics in my area (Fremont/Newark, Ca.)
>>>
>>> Any further advice on this would be appreciated.
>>>
>> I'm more concerned about the low fuel pressure than the shop is. The fuel
>> injection system is basically a reckoning system (fine tuned by the O2
>> sensor when that warms up) that opens the injectors for an amount of time
>> based on the air consumption reported by the air mass sensor and assuming
>> the proper fuel pressure. Too low a fuel pressure means too little fuel
>> injected.
>>
>> Might as well go ahead with the cleaner. If there is grunge in the system
>> you'll be better off with it dissolved off the sensitive surfaces. I
>> don't think the pump is bad - low pressure isn't its style. I'd focus
>> more on the fuel filter and possibly on the fuel pressure regulator. Any
>> competent mechanic can change the fuel filter; unless things changed
>> between my '85 and your '91 it is under the car below the driver's seat.
>> It isn't hard to change with the car on a lift but it is a pain to do
>> with just a creeper. However, I dunno about the pressure being low. At
>> least in the older 740s normal pressure is 36 psi, 43 for a turbo.
>>
>> You can also try the procedure for starting that is used when the check
>> valve is leaking (allowing fuel pressure in the rail to bleed off when
>> the engine isn't running.) To do that, hit the starter for half a second
>> or so, then let the key spring back to the "run" position. Leave it like
>> that about two seconds while the fuel pump brings the fuel rail up to
>> pressure and try starting.
>>
>> Mike
>
> Is there a way for me to test the air mass sensor, to determine if it
> needs to be changed? I just read online that its an easy switch-out.
>

If you have access to another car with the same fuel system then yes,
otherwise no, not without creating a test setup that will power the sensor
and let you read the output as you vary the amount of air blown through it.