97 850 Starts, runs and then dies when warm

Post by **scot850** » 22 Jul 2022, 20:18

Hi Guys,

On Monday I am going to help a guy out (I hope) with a 97 850 he bought for his daughter as a first car. Has about 110,000 miles on it and so far a repair shop has swapped the fuel filter and fuel pump and the issue persists.

I am going to take a spare fuel pump relay with me and check the usual issues of spark, fuel flow and the likes (distributor and rotor).

I also plan to check the ECT and connections. Plan is to at least hopefully get it running reliably enough to get it to may garage about 20km away so I can then give the car a thorough going over and list any potential other issues as well as getting it to run reliably. Unfortunately his daughter has not been able to drive the car yet which is a shame.

Any other suggestions on the start, runs ok till warm and then dies would be appreciated!

Unfortunately so far I have not had a -98 car long enough to get either my Vol-Fcr to work or my ELM and 850 OBD on my phone. I will also take my OBDII Autel 802 which reads codes on my friends 98 Volvo V70.

Thanks,

Neil.

Post by **abscate** » 23 Jul 2022, 01:44

Fuel pump relay a good bet! Bring your fuel pressure gauge to confirm!

Post by **foggydogg** » 23 Jul 2022, 13:14

That does sound like a classic capacitor failure in the relay scenario.

Post by **scot850** » 23 Jul 2022, 13:46

That is what I was thinking/hoping, might take a MAF with me too, as that also is what happened with my friends V70 NA (98). Ran to the end of the lane and lost power and died. Removing MAF cable proved that. Now replaced and so far so good 2 months later.

Neil.

Post by **erikv11** » 23 Jul 2022, 14:40

Shhhh don't tell abscate you tested a MAF that way ...

I'd pull the cap and take a look, especially if it's an NA where access is so easy. To check out two possibilities - blown rear cam seal (e.g. causes moisture to accumulate after a bit of running), and pitted/bad contacts (resistance gets too high once temp gets up under the cap leading to no spark). Even bring a spare cap/rotor if you have one I suppose.

Post by **scot850** » 23 Jul 2022, 15:29

Hm...I may well still have -98 cap and rotor kicking around!! Now they are where???

Neil.

Post by **abscate** » 23 Jul 2022, 18:37

I’ve got a spare if needed

rrres · Post by **rrres** » 24 Jul 2022, 00:31

Since you'll have a reader / scan tool, betting you'll be able to figure it out. I'm sure you'll replicate when it dies...then read the data for any anomalies. I'm still new to the Volvo world, so this is just a suggestion, but I would look at sensors that go into close and open loops...the first one that comes into mind is the O2 sensor. Maybe when the engine warms and puts the O2 sensor in closed loop, the sensor, if defective, gives a crazy reading that throws the F/A ratio out of wack...making the engine die.

Post by **abscate** » 24 Jul 2022, 01:04

Disconnecting the MAF and forcing open loop running is a perfect way to diagnose a fuel air mix problem, it just doesn’t point to the MAF as the culprit, but Professor Potato knows that already.

Visual inspection of plugs, cap, and rotor

Little sniff of ether if you can get it to stall, or fuel pressure monitor during running ( I’m still smarting pain after measuring 65 psi pressure on an empty saddle tank)

Bring a spare 1998 coil for swap , too.

Post by **scot850** » 24 Jul 2022, 09:00

Thanks for all the suggestions which I will take along with me. Only thing I am certain I don't have is a coil. I got rid of a lot of my 8 stuff or sold it on as I don't need it. What I still have is now only as I look after a 98 V70 NA.

The suggestions help me to plan what to take, hardest part is finding any of it as my garage contents are in a huge pile in the basement due to the floor being sealed/painted in the garage. I guess I know what today's plan is................!

Neil.