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760 problems help please

855 views 4 replies 3 participants last post by  freedomrock 
#1 ·
On the way down to the beach my 1990 760 turbo starting giving me problems. The rpms would drop to nothing and then come back up(motor dying off). Sometimes it would dye completely for a couple of seconds and then back on. And sometimes i would have to turn the key on and off(not turning the starter) and it would come back on with the car still in drive.

I talked to a Volvo tech and he said that they had problems with the mass air flows in them and that he though it sounded like a mass air flow problem, and that i should start there. So here is the diagnostics i did on it.

Checked for battery voltage between terminals 5(blue/yellow wire) and a good ground, and between terminals 5(blue/yellow wire) and 1(brown wire) and i did have battery voltage there.

Next check i did i checked between terminals 2(blue/green wire) and terminal 3(blue/red wire) for approximately 3.7 ohms and i was getting 3.2 ohms.

I then checked between the number 2 terminal(blue/green wire) and terminal six for around 0-1000 ohms. I was getting nothing on my DVOM so i have an open there.

So i assumed the mass air flow was bad so i went and picked up a new 315 dollar one. I did the ohm checks on the new one and still had apparently an open between terminals 2 and 6.

The owner of the small dealer i went to wouldnt take it back because i toke it out of the box. If someone knows for sure that there should be resistane between those two termainls let me know because i will make the guy take the part back or give me a new one.

A couple thinks i would like help with please:
First are my checks right and do you know of anymore i could have done.

Second does anyone know of this symtom and know what else i could check to take a look at.

Any help or suggestions would be the best thanks.
 
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#3 ·
Re: 760 problems help please (kerlizm)

I don't know how much help I can be but, my 740 turbo has had similar problems. Very similar. When driving along, my RPM's would stutter and then shut off or either rise back up to operating level. I had no clue what was wrong and took it to my mechanic. he replaced about $2000 in parts/service and it runs like a champ, but still acts like that from time to time. I had him keep it for a few days to diagnose and they let it idle all day one day and nothing happend. Then the day I went to pick it up, it was idling and as soon as I paid and got the keys it shut off. needless to say, they kept it for a few days. We came to the conclusion that the main or branch harnesses are going bad. Not sure which one, but my only "permanent" fix is to replace them.
 
#5 ·
Re: 760 problems help please (kerlizm)

I recently bought a 1987 760 turbo. After 3 months it started similar problems and finally just would not start. But, it had fire and fuel, I could smell it. What I found was that the fuel pressure regulator had gone bad and fuel was being pumped directly into the intake manifold through the vaccum line. Maybe this info might help you.
 
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