'98 S70 Jerky hesitation Topic is solved

[dosbricks]

Thanks, gentlemen. I will do as advised after driving the car a few more days with the jumper in place, then swap in a good relay if all is well (drove it tonight and it ran fine). I ordered a new seal ring with the pump. Thanks for the link! I'll report back on the eventual outcome.

dos

[MrPc]

When my fuel pump failed this past winter, it didn't make any noise at all. Before I removed it, I noticed that tapping on the pump with a screwdriver handle would start it running again.

I replaced it with a junkyard fuel pump to get it back on the road quickly, and ordered the insert kit from FCP. When I went to install the insert in the original pump, I found that the wires inside the fuel tank had deteriorated where they're soldered to the conductors that span the fuel pump "lid". Applying 12V from my battery charger directly to the pump terminals itself gets it to spin just fine.

As an aside, I followed the instructions with the fuel pump insert when I installed it in the original fuel pump assembly, but I don't like the way it flops around. It seems like the only thing that's holding it up off the floor of the fuel tank is the short piece of fuel hose and it's free to move around within the assembly. Has anyone else noticed this, and been bothered by it? I wonder if this contributes to the increased noise some have reported with the new inserts. I haven't installed it into my car yet because of this. The junkyard one is running fine in the meantime...

[sleddriver]

...Misha, I've always been curious, what exactly does the fuel damper do? Is it something we should all start replacing as we approach year 20 on our cars?

It absorbs the pulses which injectors are making.
When fuel pressure damper fails,injectors becomes very loud.That's the only side effect besides obvious leaking.
No need to replace it if injectors don't make loud ticking and if it's not leaking.

Bingo....the injectors on my car have always been quite loud. Never could understand why until I read the above. Thanks for posting this.

[dosbricks]

OP situation report:
I have been driving the S70 for about 5 days with a jumper wire in place of the the fuel pump relay. Yesterday was the first occasion to get it out on the freeway for about a 40 mile run. It produced about a dozen very brief hiccups at highway speed and always when cresting a hill or slightly backing off the accelerator--never under acceleration. So I'm in the process of swapping out the pump motor insert. I'll report back the results after test driving a few days.

The car was running lousy with 2 different relays in it. Any thoughts as to why it runs 90% better with the jumper wire in place, but not 100%---maybe pump just weak and the relay creates a little extra resistance?

dos

[bmdubya1198]

That almost sounds like crank sensor symptoms...

[dosbricks]

I actually had the same thought, but would the relay jumper improve it if it was? If the new pump doesn't do it, I have a good used CS to swap in there. Anyway with this cars mileage, it was time to change the pump.

[bmdubya1198]

I agree, it would be good preventive maintenance anyway.

[sleddriver]

Dosbricks: Verify the wiring insulation on both the crank & camshaft position sensors is intact. The insulation can turn to goo, resulting in bare wires, that can easily short causing all sorts of intermittent engine running problems due to vibration. Also verify the wire insulation on the main harness side of the wiring connector is intact. .

Finally, be sure that the spark plug wires & coil wire are as far as possible from either of these sensors and their wiring! The HV pulses will induce currents into the sensor wiring that will annoy/confuse the ECU. The worse possible combination is to have the coil wire close to either sensor wiring & parallel! Separate as far as possible and orient them perpendicular to minimize induced currents.

This should be a mandatory check on any old Volvo that runs poorly, jerks, hesitates, stalls, is hard to start, etc. Often the fuel pump & relay is blamed instead.

[WhatAmIDoing]

I am experiencing similar issues. Thought it was just the fuel pump relay (was partly true), but turned out my cap and rotor was bad (and possibly more I haven't discovered yet).

[dosbricks]

Problems!!
In an April 9th thread titled "P80 Fuel Pump Insert (Bosch) on sale at Rockauto!" it recommended the Bosch 69693 pump insert for our cars. I'm posting here what I just posted to that thread.

DO NOT BUY a Bosch 69693 for Volvo 850 or S70. It does not fit because the diameter of the plastic barrel on the pump is about 3mm too large to fit in the plastic inner shock assembly on my S70. It is also too long to fit that assembly. It has taken major modification of that assembly to make it work which has turned this job into a huge hassle. I won't know that it will work until I have it all back together. I'm not even going to go into what mods I did because it's too complicated.

FCP lists the Bosch 9438003 as being the correct insert for the 850 and S70. They do list 69693 as being an alternative part number, but I'm here to tell you it won't fit. Maybe it has the same gpm rating (which I hope) but it is for sure made for a different vehicle.

I jumped out too soon on ordering this pump because of the great price, and without doing the proper research. I'm taking a chance because the car is apart and I don't want to wait another week with it down. If I ever do this job again, I will order a complete assembly.

And BTW, 12" of Gates submersible 5/16" fuel line to replace the 5" piece that connects the pump to the outer casing costs $30---which just ads insult to injury!