help needed 1998 V70 warm start problem

[ka0ren]

Hi, 1998 V70 Non-Turbo auto trans. Starts perfectly when sits overnight. Shut it off when warm and engine cranks, but no spark and no injector pulse. Fuel pressure O K. Have tried new ign/ coil module, has new plugs, wires, dist cap & rotor,have removed ECU and sprayed DEOXID on terminals, have subbed crank posn sensor and cam posn sensor from running car = still no start until perhaps 20+ attempts donor car starts right up with V70 parts]. When car starts can drive 300 miles [ if not shut off !] Fuel mileage 28 hiway, NO MIL or codes using VOLVO scan tool. Any ideas ?

[SuperHerman]

Did you check relays for all related systems?

[ecbsykes]

So it only has trouble starting when warm? Could be the ECT acting up and giving bad signals maybe.

[scot850]

+ 1 with ebsykes comments. Based on the symptoms, I would check the resistance values of the ECT (water temp sensor) that is mounted below the thermostat housing. The connector to this is usually mounted on the back of the power steering pump. Also check the connector at that point as the wires and connection can start to fall apart with age and heat from the engine. Somewhere on MVS there are resistance values based on ambient external temperature over a range.

There are aftermarket parts but this is one I would recommend the OE Volvo part. There is I think one aftermarket option some have had luck with but I don't recall the brand.

Neil.

[misha]

...There is I think one aftermarket option some have had luck with but I don't recall the brand...

It's Vernet.

[mrbrian200]

Being thorough here- also wouldn't hurt to check your fuel pump and engine system relays. Recently aware of a friend of a friend having trouble with his '04 V70. Sometimes he'd start it, it wouldn't idle, sometimes limp mode, more often when hot. It got to the point where he couldn't drive the car anymore for work (delivery for a restaurant). Restarting the car several times and/or disconnecting the battery cable it would usually 'clear up' and then run/drive normal--until he'd shut it down and try to restart it. One of the under hood relays had worked itself partially up/out of it's socket. I don't know which one. He found it himself, said more than one wasn't seated, he pushed down on all of them and hasn't had an issue since.

In your case it sounds very consistent - if the primary relay coil is 'weak' due to either a failing coil or resistance in the connection to the plug/socket, the magnetic flux/pull will be weaker when hot (this is the nature of magnetism both permanent and electromagnets) and maybe not be strong enough to close the electrical contact.

[scot850]

Thanks misha. I just couldn't remember the brand name, and coincidentally I had a call from a Volvo owner today on the same subject with a low reading/non-starting V70. I can now send him the info on that brand assuming it is available locally.

Neil.

[ka0ren]

Getting harder to start when warm. Replaced relays [ fuel pump and main] no difference. With technician's help, determined no injector pulse and no power to ignition module when cranking [ warm engine] Fuel pressure normal . New battery 730 cca but did not help.

Any ideas if the immobilizer can cause these symptoms ? Have 2 other 1998 70 series cars with no problems [ swapped parts back and forth but nothing solved = donor car starts and runs fine & problem car still does not start.

[scot850]

Did you check the coolant temp sensor as suggested? If so, please let us know or we will go around in circles.

As this is a non-turbo, have you checked the cold start air-flap in the air-box to make sure it is not stuck in the cold position? If it does it will feed only hot air to the engine which may fool the sensors.

Neil.

[ka0ren]

Back at problem -crank-no start when warm . Starts first time . WILL NOT restart even after being run 2 minutes. Tried subbing ignition switch and antenna ring from nice running S70. NOTE: SW70 starts and runs with antenna ring disconnected. Subbed ECU still cranks, no start. Checked coolant temp sensor test 1,340 ohms at 114 degrees F . S70 CTS tests 1,180 at 104 degrees F. Will pull spark plugs next to see if dry or wet, but NO fuel smell from exhaust [ no injector pulse ]