1998 V-70 T-5 Cranks but no-start after running OK

[abscate]

It doesn’t sound like a Sensor but Diagnosing by symptom is unreliable.

Can you describe what “ low compression starting ‘ sounds like? Does the cranking change or is it just not firing?

Fuel pump relays on high mileage cars get iffy and temperamental; that’s an easy swap with a junkyard one

[reluctantmechanic]

I don't think it is a fuel pump relay. The engine never cuts out while driving it.

What I referred to a "low compression sound" when starting is when the engine spins while starting it is as if the valves, some or all, are held open, and the engine encounters little or no resistance when cranking. It almost sounds like the starters bendix drive is not engaging. The engine uses little or no oil, btw.

The cranking sound changes. Usually, when I crank the engine, it will fire up within 2 seconds, almost instantaneously. Under the conditions of what I have described as "low compression sounding," the engine has to be cranked continuously, for longer, perhaps 5-7 seconds; the sound is at first, normal (like the car wants to start) but it does not, the next few second of continuous cranking the engine sounds like starter is not engaged because the sound is like low compression, but eventually, if the cranking is not stopped, the car will fire up. So, if the engine doesn't fire in the first two seconds, and I continuously crank it until it fires, this is what it sounds like.

I've read of others having the symptoms of their Volvos running fine, shutting the car off after operation, then trying to start the car after 20 minutes and the car not starting. This is the symptom I have experienced. Thanks for trying to answer the question.

[abscate]

That sounds a bit like lawn mower syndrome. Excess gas washes down the oil in the cylinders and causes low compression. It’s usually caused by a marginal Engine coolant temperature sensor Which then commands too much gas injected ona warm start.

Diagnosis. Get out the ohmmeter and compare the ECT resistance to specs. Examine wiring for green crud of death and corrosion.

You will get experienced mechanics tell you lawn mower syndrome is fiction. It isn’t.

[RickHaleParker]

It was about 18 degrees F that day, fwiw. He has looked at it and tells me there is plenty of fuel pressure, so I asked what could be the problem.

My 1998 C70 won't start when it is that cold. The barometric pressure sensor craps out at them temperatures ( AKA Altitude Sensor (MAP Sensor ). A shot of either will get it started.

Barometric pressure is one of the data points used to calculate fuel charge. Generic OBD scanners will not read the barometric pressure sensor DTC code. I used either 850 OBD-II or VOL-FCR to catch the error code not sure which one of the two.

I know I need to replace the barometric pressure sensor just never got around to it. They sell for $71.49 - $161.49 at FCP Euro. Volvo part number 1275342.

Don't quote me on this but, from the data it appears to be the same sensor used for the MAP sensor on the P80s. Only difference is the barometric pressure sensor is exposed to ambient pressure and the MAP is exposed to manifold pressure. You could try pulling a MAP sensor out of another P80 and try it as a Barometric pressure sensor on yours.

[reluctantmechanic]

Hi Abscate and RichHaleParker

Thank you both for your time and advice.

I had the opportunity to listen closer to the starting sound, today. I believe it is the "bendix drive", dropping out when the engine is cranked for a few seconds. What clued me in was when the drive failed to engage from the initial key turn, today. When I tried again after a few seconds, the drive engaged the flywheel and it started up within a second or two. The car has not failed to start since I have been using it over the last 2-3 days.

I will ohm out the ECT.

Thanks again and I'll report back.

[RickHaleParker]

When I tried again after a few seconds, the drive engaged the flywheel and it started up within a second or two.

Check the bolts on the starter. If they are loose that can happen ... Starter get a little out of alignment.

[reluctantmechanic]

Greetings
The saga continues.
The car failed to start and exhibited the same symptoms it did a year ago.
This time, it "threw a code," the scanner indicating " P0340 Camshaft position sensor, bank 1 circuit malfunction."
Because the car would crank, had fuel pressure but no spark, I figured it was the cps, but I'm trying to confirm it.

1. using an ohm meter setting I "rang out" all possible combinations of the wires going to the sensor. There was no continuity indicated. Does this mean that there is a break in the winding in the sensor? The connector to the cps was crumbly. (I'll attach photos if possible)
2. When I disconnected the sensor from the plug going to the wire loom, there appeared to be greenish grease-like substance on the locations (female side) the sensor plug's pins (male side) enter. Is this some form of dialectric grease?
I cleaned it out with a q-tip covered with WD40 but I didn't spray the connections.
3. When I removed the air filter box to get at the connectors, there was junction block for vacuum hoses attached to it. the lower hose was disconnected and without a readily visible place where it should be connected.. Maybe someone can tell me where it goes; I'll try to attach photos.
4. I realize that there is a way to "back probe" the wiring to the car's computer. I didn't have the instructions with me today, so I didn't do it.

[scot850]

That green stuff is brass contact corrosion. Use an old tooth brush or brass brush with contact cleaner and clean all that stuff off. It acts as a barrier to electrical parts getting current. Check the one on the MAF as well. It is likely the same.

Sorry not sure where that pipe goes on a 98.

Neil.

[abscate]

That’s the boost control valve for the turbo. That probably is the “ blue “ hose that returns boost pressure to the snorkel

Red hose brings pressure from the turbo casing
Yellow sends sends pressure to the wastegate actuator
Blue returns to snorkel

* the hoses are all black but were labeled with coloured bands from factory.

That missing blue hose also means you have a massive vacuum leak at the snorkel which will cause your symptoms

[reluctantmechanic]

I changed the cam position sensor and the engine fired up with almost less than one full crank. So , I believe the crank no start problem has been resolved. Many thanks to everyone who helped me with it. I believe the nonconductive material holding he sensor inside the cps cap had deteriorated to the point that it affected the sensor, rendering the car inoperable. As soon as I touched it, attempting the check the conductivity of the leads, it broke. The replacement cost $125+/- and appears to have a similarly cast exterior as the original; the parts clerk telling me that it was the same manufacturer used by Volvo. How true that is, I do not know. The sensor appears to be the same, as well. (I used this parts provider because most mechanics locally use them, and they don't want to do the job twice : -)
I believe this part was failing intermittently for several years, but only during very cold days here in the Northeast, until it started doings so during the late summer. The Problem stumped at least one professional mechanic who could not resolve it.

I have yet to find the connection for the blue striped vacuum home, but I believe this problem is solved.