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93 850 the dreaded warm start problems, cranks but no start

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

93ForMe
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93 850 the dreaded warm start problems, cranks but no start

Post by 93ForMe » Sun May 17, 2020 5:35 pm

Hello everyone! I have combed through this site and found so many solutions to so many problems for my manual transmission 1993 850, and I am very grateful for what everyone has shared in the past. I am finally at the point where I am stumped and would like to ask for help. This might be a little long, but I want to give some background information on where I started and what I have fixed so far.

A month or so back my 850 started to randomly stalling out at low RPMs and would then crank but not start. It would however crank and start after letting it rest about 25 minutes, so I could always get it home. I called my Volvo mechanic and to my surprise, the shop had closed for good, so instead of finding a new shop, I started reading forums.

It looked like the most likely solution was the Fuel Pump Relay, so I replaced that.
Didn't fix it.

I started paying more attention to what was going on. As I accelerated from a stop, the power would cut out and the car would stall and not restart. Idle air control valve?
I cleaned it. It was very dirty. Didn't fix it. Found a very inexpensive used one on ebay, cleaned it, put it in.
Didn't fix it.

The problem seemed to only present itself before the engine was completely warmed up to operating temperature. I replaced the engine coolant temperature sensor.
Didn't fix it.

Cam Sensor
Didn't fix it.

Cranckshaft Position Senesor?
Didn't fix it.

MAF Sensor? I unplugged it when it wouldn't start to put the car in "limp mode"
Still didn't start

At this point I realize that I was just throwing parts at the problem, but every time I replaced an old part, the car seemed to run and drive better, so I didn't really mind because all the parts were fairly inexpensive at this point and I was learning a whole lot about my Volvo.

I pulled the vacuum hose off of the Fuel Pressure Regulator and smelled gas, so I decided to replace that.

As I was removing the fuel rail I noticed that the hose from my PCV breather box to the flame trap ( that my mechanic replaced ) was just a heater hose, saturated with oil and had no clamps on either end. It had fallen off, thus causing a huge vacuum leak, and an oil leak.

I pulled the intake, replaced everything PCV related, replaced the Fuel Pressure regulator and all the vacuum lines.

When I put it all back together, the car ran amazing! So much more power and it no longer stalled out, but the no start problem remained.

I hooked a fuel pressure gauge to the fuel rail. It goes to 44psi when the fuel relay clicks on, then drops down to 37psi when running. Fuel pressure remains good even when it cranks but won't start.

It will start just fine every morning. If I drive 2 miles, just to the point where the temp gauge hits center and turn it off, it will crank but not start for 25 minutes. If I accelerate heavily during this initial 2 mile period, the power will cut in and out. After 25 minutes it will start just fine. It will start just fine the rest of the day. It will also accelerate smoothly the rest of the day and run very smooth. I can't get it to repeat the same symptoms until the next day. I can get the symptoms to repeat themselves the next day like clockwork.

When it cranks it will catch, almost start, then cough and a puff of air will leave the exhaust and it will stop. Sometimes it rumbles a little. I didn't notice any black smoke or gas smell out of the exhaust.

If I drive for 4 miles instead of 2 and turn it off, it will take a couple cranks to start it, but it will start.

I was thinking that the problem would not be the 02 sensors because I read that before the car is fully up to temp it is in Open Loop mode for the cold operation and the 02 sensors are not used? Am I correct in this?

I am starting to think that there might be a problem with the computer? Do these computers fail in strange ways like this?

Thanks for reading this long tale. I am hoping that someone with more experience than I have might be able to make sense of this and point me in the right direction.

I have been driving this Volvo since 1992, and I would hate to give up on it!

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Jaydiesel
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Re: 93 850 the dreaded warm start problems, cranks but no start

Post by Jaydiesel » Sun May 17, 2020 9:02 pm

Just my 2 cent. but check the pos cable going from battery to starter. I had restart issues like what your talking about on my 2000 V70. and it was that cable. those cables and connections have been know to burn up and go bad.
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Re: 93 850 the dreaded warm start problems, cranks but no start

Post by abscate » Mon May 18, 2020 4:53 am

You are correct about the OXS sensors, they go closed loop after a few minutes, after they heat up.

First, are using OEM parts on all the replacements? The coolant temperature sensors (ECT) on these cars are known “ fussy” items on these cars

How about. The last time the ignition system was serviced?

Your symptoms are descriptive of a failing ignition coil module, but evaluate everything.

Coil
Wires
Cap
Rotor
Spark plugs
Spark plug wires (Bougicord only here)
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Re: 93 850 the dreaded warm start problems, cranks but no start

Post by 93ForMe » Mon May 18, 2020 11:36 am

Jaydiesel wrote:
Sun May 17, 2020 9:02 pm
Just my 2 cent. but check the pos cable going from battery to starter. I had restart issues like what your talking about on my 2000 V70. and it was that cable. those cables and connections have been know to burn up and go bad.
Thanks for the reply! I checked both ends of the positive cable on the battery and the starter and they are both tight and corrosion free.

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Re: 93 850 the dreaded warm start problems, cranks but no start

Post by 93ForMe » Mon May 18, 2020 11:44 am

abscate wrote:
Mon May 18, 2020 4:53 am
First, are using OEM parts on all the replacements? The coolant temperature sensors (ECT) on these cars are known “ fussy” items on these cars
I am. The ETC is an official Volvo part that I purchased from FCP Euro
How about. The last time the ignition system was serviced?
Last summer I was having a problem where I was loosing power during acceleration. It turned out that the cap was cracked.
The Mechanic I was going to at the time replaced the wires, cap, rotor and spark plugs. I just looked and the spark plug wires are Bougicord.
I've put around 5,000 on the car since then.
Your symptoms are descriptive of a failing ignition coil module, but evaluate everything.
What is a good way of testing the ignition coil module? I was reading that you can test the red wire for voltage, then when cranking the starter, if the blue wire pulses, then the coil module if functioning? Sorry if this is a basic question. I'm pretty new to all of this!

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Re: 93 850 the dreaded warm start problems, cranks but no start

Post by jreed » Tue May 19, 2020 5:39 am

Good luck. It sounds like you have checked a lot of things and already replaced a lot of the parts that are the "usual suspects". As for the coil, one check would be to disconnect the wires and measure the resistance of the low and high sides during the time that the car will not start. According the the Haynes manual, the coil primary should read between 0.5 to 1.5 Ohms and the secondary should read between 8000 and 9000 Ohms for 1994 and on. I recently checked my spare coil (from a '96) and got values in that range so I think you should see similar values on your coil. For pre-1994 B5252S engines, the primary resistance is "not specified" and the secondary should be between 6000 and 7000 Ohms.
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Re: 93 850 the dreaded warm start problems, cranks but no start

Post by 93ForMe » Tue May 19, 2020 12:32 pm

jreed wrote:
Tue May 19, 2020 5:39 am
Good luck. It sounds like you have checked a lot of things and already replaced a lot of the parts that are the "usual suspects". As for the coil, one check would be to disconnect the wires and measure the resistance of the low and high sides during the time that the car will not start. According the the Haynes manual, the coil primary should read between 0.5 to 1.5 Ohms and the secondary should read between 8000 and 9000 Ohms for 1994 and on. I recently checked my spare coil (from a '96) and got values in that range so I think you should see similar values on your coil. For pre-1994 B5252S engines, the primary resistance is "not specified" and the secondary should be between 6000 and 7000 Ohms.
Thank you for this! It is very helpful. I just tested my coil cold and then warm after about five minutes of idle when the engine started to get rough.

Cold
Primary 0.7 Ohms
Secondary 8,500 Ohms

Warmish
Primary 0.7 Ohms
Secondary 8,900 Ohms

I do think that this coil is the original one currently in my 1993 850. This would mean that the resistance would be higher than spec, which I believe would cause the voltage to drop leading to weak spark? I read that when the car is cold, it is more difficult for engine combustion to take place. Perhaps this is why my problem only occurs when warming up and seems fine when it comes up to full operating temperature?

I purchased a working coil from a salvaged ( due to accident ) 1998 S70 on ebay for a very good price. I did match the part number with compatibility and from what I can find, it is compatible with a 1993 850. I will put it in as soon as it arrives and report back my findings.

Thank you again!

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Re: 93 850 the dreaded warm start problems, cranks but no start

Post by misha » Tue May 19, 2020 2:03 pm

jreed wrote:
Tue May 19, 2020 5:39 am
...For pre-1994 B5252S engines, the primary resistance is "not specified" and the secondary should be between 6000 and 7000 Ohms.
How is that?!
Ignition coils are ALL the same for ALL petrol 850 and s,v,c,xc70 (with cap & rotor)up to '99...and all have the same specs.

In '99 with introduction of ME7 cap & rotor became history and Volvo switched to coil packs.
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Re: 93 850 the dreaded warm start problems, cranks but no start

Post by jreed » Tue May 19, 2020 2:13 pm

The values are from the Haynes manual... I'm not sure if they are correct or not, but that's what the manual lists on page 5B1
Screen Shot 2020-05-19 at 4.12.16 PM.png
Screen Shot 2020-05-19 at 4.12.16 PM.png (79.44 KiB) Viewed 112 times
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Re: 93 850 the dreaded warm start problems, cranks but no start

Post by misha » Tue May 19, 2020 2:26 pm

Hmm....all ignition coils are completely the same...same part#,same specs from '92-'97(including '97)850 and across s,v,c,xc70 from '97-'99(excluding '99).

It is probably the management which outputs different values to the coil for 10v cars(B5252).
'97 850 2.5 20v / fully equipped / Motronic 4.4 from the factory / upgraded with S,V,C,XC70 instrument cluster / polar white wagon
'91 Citroen XM 2.0 SI /fully equipped/mandarine red metallic
History of Volvos in the family:
'71 144 S
'73 144 De Luxe
'78 244 DL
'78 244 DL
'79 244 GLE
'85 340 GLS

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