'87 740 won't start after fuel filter replaced
 

New to Volvo's - mostly worked on Toyota's, but my girlfriend has a 740 w/ a B230FT engine w/ 219k miles.

It had been seeming to misfire and lag at various times while driving and she said it got more frequent. It never did it when I was driving it. Finally died and I replaced the fuel filter - the under car fuel pump (Main Fuel Pump?) was changed last year with a good Bosch unit.

After install it started up and ran well and then after shutting it off, it wouldn't start later. It acts like it's not getting fuel. Cranks, catches, but then doesn't continue. The tach registers.

I've seen various threads suggesting Fuel pump, coil, ECU, AMM, IAC, blah, blah blah...I have two different Haynes manuals, but am disappointed in the quality of the info.

Is there OBD on an '87? My Haynes manual has nothing.

My GF's mechanic says the car should run even if the in tank fuel pump is bad. True?

Thanks!

No OBD on 87s...
Should run on main pump only...
Fuel filter had nothing to do with the problem...
How are the "tune up" items, plugs wires, cap, etc?
Spray some ether in the intake to verify if fuel delivery is the issue, I doubt it...

Get moving?
 

You don't have obd2. On my 89 i could make a light blink on the instrument cluster to get diag feedback. That said, the Haynes for that year was the same book and if your serial number build had the capability the manual will help.

That said, you might not need the diag although it wouldn't hurt.

Remembering my 89 745 here are some insights.

The air intake duct, is it soft from oil? If it is soft enough it can collapse and cut off air while running, making the car quit. If the AMM reading is too low the ECU will turn the car off. Have someone start it while you watch the engine.

A worn out air mass meter will go intermittent before failing outright. You'd be able to crank and catch but the car would not run, it would stall. I remember something in the Haynes on how to check AMM but do not remember if it was using a DMM or an oscilloscope.

Albert

So the AMM was apparently replaced last year and there is also a replacement ignition relay that was part of a previous stalling problem. The noise suppression relay was also changed last year.

It appears that the coil is fried. Primary resistance is zero 0.00 and secondary is 10.0. One of the primary leads appears like it over heated and most of the insulator is melted of and it is mostly burnt copper.

So the distributor wire from the coil is fried also as its' resistance is 2.75 kOhms.

Plugs are fouled some and the rotor cap and rotor are ready to be replaced.

BUT...what causes the Coil to fry the wire like that and what damage happened to the rest of the ignition system? What's next?

Also just noticed that the 2 wire connectors that plug into a sensor on the radiator is having a lot of cracking on the insulation. Seems odd that it would crack from aging - this car was overheating when I first started riding in it and it turns out the mechanic only had a 14 psi pressure cap on the reserve when the engine type calls for a 21 psi (230FT). He claims it shouldn't make a difference, but as soon as we changed it to a 21, it stopped overheating and blowing all the antifreeze out the reserve

89+ non-turbos and 90+ turbos have LH 2.4 injection with OBD-I (not -II). prior to that, they were LH2.2 with no real diagnostics.

the temp sensor on the radiator is only used for the electric fans, I believe. the fuel injection, ignition module, and dashboard temp gauge use temp sensors under the intake manifolds.

I don't have wiring diagrams on 740's older than 1991, but I believe the ignition uses an ignition power module mounted somewhere under the hood, this power module drives the coil. the power module in turn is controlled by an ICU mounted under the dash, I think on a 740 they are behind the glovebox but I could be wrong, it might be behind the dashboard, above the pedals.

all volvos from around 1982 or 83 to mid 1987 suffer from 'biodegradable' aka 'ecojunk' wiring insulation. the harness insulation hardens, then cracks and flakes off, most often inside the black sheaths where you can't see it.

+1 for Pierce - more directly, the right short would fry your coil. That harness repair will take a while.

Try replacing the Radio Suppression relay that is mounted to the coolant overfill tank on the left side of the engine compartment.This relay controls the fuel injectors. Also check the crank position sensor connector.