Hey all, new forum member here.

I've run into two problems simultaneously that I just can't figure out.

It's a non-turbo 1993 940.

First thing, when I start it in the morning and after work, I have to let it run and 'warm up' for about 10 minutes (even if it's over 70 degrees outside) or else when I go to drive it, it will hesitate and shake and rumble when I start to accelerate and not be able to go over, I don't know, maybe 3 miles an hour. I will have to pump the gas repeatedly until it catches up and starts driving like normal but it will happen again if I stop at a street corner and go again. However, if I DO let it warm up for 10 minutes, it drives beautifully with no problems.

My second problem is that only AFTER I drive somewhere and shut it off, I won't be able to start it again for about 5-10 minutes of waiting. I will turn the key and it will start and then immediately shut back off again. If I keep trying to start it, it will either just crank and not turn over or it will turn over and grumble and shake and then just shut off again. Pushing on the gas while starting makes no difference. After 5-10 minutes of waiting, it will start just fine and drive just fine. This gets really frustrating and embarrassing when I'm stuck at the gas station hogging one of the lanes because I can't move.

I don't know what to make of it. I've recently replaced the fuel pump relay, the fuel injectors, the alternator, the battery but I'm still having these problems.

Has anyone also experienced these problems or does anyone know what else I should check? I would greatly appreciate it as this is just killing me. I love this car, I just want it to work!

 

1. Change the Coolant Temperature Sensor- It is sending the wrong signal to the computer NOT to send extra fuel which the car needs as it starting from cold and it needs the extra gas, like a choke, sort of...

2. Change the Fuel Pressure Regulator--It is not holding pressure as it is supposed to, affecting your warm starts.

 

That's pretty excellent advice. Thanks!

Any tips on replacing the coolant temperature sensor? It seems to be in a pretty hard place to get to without taking off the manifold above it.

 

It is a bit challenging, yes... Small hands help; unclip the connector, then use a long extension with a 19mm socket in a straight shot. Don't worry about the coolant loss--it's minimal. Or you can remove the intake manifold if you need to service that gasket and the oil separator. It is really not that hard. I am doing an EGR valve on a '95 right now and it is the same procedure so I do everything at once. Do you have an EGR valve? Some '93 do... and they need to be serviced every 60k or so...

 

I actually don't believe my car has one. I've poked around a bit and wasn't able to locate one.

Unfortunately, my car has the rex regina system and I can't find the fuel pressure regulator I need for it anywhere even on the vastness of the internet and none of the local stores have it. Pretty frustrating. Everywhere that has it on their website says its unavailable when I go to check out.

I'll give the coolant temp sensor a shot though and hopefully that will get rid of one of my problems.

 

my parts catalog says the reginal fuel pressure regulator is Volvo PN 6842410 which.... OUCH is 'no longer available'. Pressure regulator. no longer available made by Volvo OEM. #6842410

hmmmm.

 

Yeah. That is such a bummer. Thanks for checking though!

If I don't have any luck, I guess I'll be making a trip to the local junkyards in the morning in the hopes that I'll find one that's still working.

 

Yes, your car has one! The CTS is under the third runner of the intake manifold.

The FPR, I have used Bosch ones in Reginas successfully, no problem! Those should be readily available--they are just bigger...

 

I meant the EGR. I know I have a CTS. I just didn't have the proper tools to do the job today. Got a new socket to fit it tonight and will replace it in the morning.

That's interesting about the FPR. If you say so, I'll go ahead and get the bosch one and see if I can make it work.

 

Yep, the Bosch fit perfectly. Installed both parts tonight and will be taking it for a test drive in the morning to confirm that it all works out!!

 

So, I started it this morning and it ran fine in idle for about 5 minutes and I turned it off and let it sit and turned it back on again... and now it won't start at all. It cranks but won't even turn over anymore. What gives? Any suggestions?

 

Does it start now, cold? You ran the car after installing the FPR and the CTS, then no start?

 

same as any no-start, figure out if its fuel or spark, then start down the trouble shooting tree eliminating things via testing.

 

So far it starts just fine cold but not warm. I can't tell if the new FPR made the warm start problem better or worse. Before it would cut on and die immediately a couple of times and then just crank until cold. Now, it only cuts on and dies once and just cranks until its cold again.

Would anything else besides the FPR cause problems with a warm start?

 

Unrelated to the parts changed, the Crank Position Sensor, and Fuel Injection relay are known to cause these kinds of warm no starts--they get hot, they short out, once cool they are OK...

I hate to "throw' parts at a problem... Based on your descriptions, the FPR was probably not the cause of your warm no start. This is the problem diagnosing like this: there are several possibilities, you go with the most common, but it's not the only one. I have a ton of parts that "known good" and when I have a problem I swap them around, it doesn't take long... But if you don't, as most normal people, it's frustrating to have to buy all this stuff.

 

Okay, that's interesting and neither sound terribly difficult to replace. It is a little frustrating just changing part after part but at least in the long run replacing old parts with new ones can only help.

Before I dive into these two parts, would any other issues cause it to fail on a warm start? I feel like I'm running out of things to change and I at least have to be getting closer to the root of the problem.

Thanks for your help!

Edit: As a follow up question, is the fuel pump relay the same as the fuel injection relay?

 

yes, on all LH bricks except the 94-95 non-turbo 940, the fuel pump/injection relay is a single relay with two seperate halves inside, one half powers the ECU, and hte other half powers the fuel pump. on 740/940's, there's an additional relay under the hood known as the 'radio suppression relay' which provides the power to the fuel injectors themselves.