Hey guys. I'm having a meltdown trying to diagnose a starting problem. The car is a 1993 Volvo 940, with the Rex Regina fuel system. The car runs fine, but after shut down, and the car sitting for about ten to fifteen minutes, she doesn't want to start. I've narrowed it down to being a fuel problem. Spraying starter fluid into the air intake starts her up and then she runs fine again.

My fuel injector relay and fuel pump relays both seem to be functioning as they should. I've read a few things about a cold start injector and an engine coolant sensor as possible culprits. I've also read that some 940 Volvos don't have the cold start injector, and i can't seem to find one on mine.

I'm wondering if either of these components are at fault. In the Regina system, is there some sort of primer somewhere that might not be working? As i said, once the car is started, there are no problems. And if i turn the car off, I can start it right back up. It's only when it's been sitting for around ten minutes. Thanks in advance for any help!

 

Change your fuel pressure regulator and your problem will be solved.

 

I just put one on order. It seems like a fairly easy DIY repair. Thanks a million. This has been driving me crazy for weeks.

 

Before you go throwing parts at it, some diagnosis would be in order. While I'm not familiar with the Rex Regina system, the symptoms you describe can be easily caused by a flakey fuel pump relay. Over time these relays develop bad solder joints and can become intermittent.

This is real easy to diagnose. When you turn the key to the II position, you should hear the fuel pump run momentarily and then shut off. Take note next time you start it. Then, when you have the no-start condition, see if you hear the pump run. If you don't hear it, then most likely the relay is the culprit. You can actually re-flow the solder joints on the relay if you have a soldering iron. Just search the forum here for the location of the relay.

Good luck

 

I put in the new Fuel Pressure Regulator and it's still having the same problem. The relays are all known to be working and you can hear the fuel pump engage. I'm back to wondering about the Engine Coolant Sensor. Anyone have any experience with these?

 

I've diagnosed ECT's on bosch systems, but never on regina. they are a simple temperature senstive resistance to ground. the Bosch ones are relatively high resistance when the engine is cold and relatively low resistance when its hot, quite easy to test with an ohm meter. I test them at the ECU, by unplugging the ECU, then finding the ECT's pin in the ECU plug, and measuring the OHMS from that pin to ground (which is, handily, another pin on the ECU plug).

note the ECT is actually a DOUBLE thermo-resistor, the other one goes to the ICU.

ok, the greenbook says, on a 1993 Regina MFI 940, the ECT goes to pin 13 of the ECU connector, and pin 5 is ground. hey, thats the same pins as Bosch LH2.4 systems!

on the ICU of a Rex-I ignition, its pin 2, and pin 20 is a ground. and thats the same pins as the EZ116K Bosch ignition.

each of these thermistors should be 6000 ohms at freezing, 2300 ohms at 20C(68F), 600 ohms at 60C(140F) and 190 ohms at 100C(212F). all values +/- 10%.

if it measures open or short, I'd suspect the wiring as much as the actual ECT, under those conditions, I'd unplug the connector from the actual ECT, and measure the resistance again at the ICU or ECU connectors.

more info on this here, Engine Sensors

 

Well, i'm getting the proper reading off of the Engine Coolant Sensor, but not at pins 13 and 5 at the ECU. I am, however, getting the reading at 2 and 20.

 

ummm, sure you're looking at the ECU (fuel injection) and not the ICU (ignition) ?!?

on the Regina ECU, pin 20 is the coil for the fuel pump relay (grounding it turns on the fuel pump relay if the FI relay is on), and pin 2 is the idle switch, which is grounded if the throttle is at idle.

when you test the ECT, you want to do the test when the engine is hot, and again when its cold.

 

I am surprised that the FPR change didn't fix your warm start problem. I have had several of these situations and the FPR has been the culprit every time. If the car starts COLD then your temp sensor is OK. Once the car has run, and it is at operating temp the temp sensor is not involved. The FPR then maintains fuel pressure and gets things going.

 

I'm surprised too. After you mentioned it, it seemed to make total sense. On the bright side, it's out of the equation now. I'm running out of things to check. Here's where i'm at:

Checked Radio Suppression/Fuel Injector Relay
Checked Fuel Pump Relay
Replaced Fuel Pressure Regulator
Replaced vacuum hoses

I've kind of ruled out the fuel pump and filter, as it never happens while driving, and only in the situation described in my first post.

And i was checking the ICU, under the steering column kick pad. Is the ECU in the engine compartment?

 

on my 1992 740T, the ECU and ICU are both on the right side footwell, against the inside fender, but these are Bosch. I've never seen or touched a Regina car, don' tthink they are very common in California. on our 1987 240, the ignition control unit is under the hood just behind the right headlight, on the fender, while the ECU is where it is on my 740.

 

Hondas a symptomatic for this problem at the ignition relay that feeds the fuel pump. If you get stuck somewhere and can't restart your car, you can 'tap' on the relay or bang on the left side of the dash in front of your left knee and usually start the car. I'd double check the fuel pressure relay... This always happens with age of car and humidity- a recent rain causes the points in the relay to stick.

 

I made sure to go over the relay a few times and it seems to be functioning as it should. I bypassed it during a no-start to no avail. Thanks for the insight though!

 

After more reading, I keep coming back to a few things:

1. Faulty fuel pump (But why only when the car sits after driving?)
2. Faulty ICU
3. Faulty ECT (Although per Pierce's advice, it seems to be reading okay)
4. The presence of demons in the fuel system

I've unplugged the Cold Start Injector in a no-start situation and nothing changed, so if i'm thinking correctly, that's out of the equation. I'm not pulling any fault codes out of the OBD. I hate to shotgun parts (as does my wallet), but i'm pretty stumped.

 

another one is to unplug the MAF during a no-start. if it starts without the MAF plugged in, then you have a bad MAF (just because its new does NOT mean its good). DO NOT PLUG OR UNPLUG THE MAF WHILE THE IGNITION IS ON. Note that without the MAF plugged in, it may start, but you can't drive it, giving it any gas will undoubtedly stall it.

ignore the above. Regina doesn't HAVE an MAF/AMM at all. It uses an intake air temp sensor, and a throttle position sensor to determine the mixture.

 

From experience, just because you change a part, it doesn't mean that the part is completely eliminated ad a suspect--once I went through four MAFSs before one worked right...

You Cold Injector is not the problem as it is for cold starts only, and you have a WARM START problem; the two are different as there different condition that we are dealing with.

Per your initial post you say that when faced with failure to start, Starting Fluid gets you going, that's indicative of lack of fuel, not lack of spark. How then, can we blame the "computers", unless somehow the computer heats up and does something weird to the injection? When stumped, often that's the first suspect, but rarely are the computers at fault in these cars.

 

a hot fuel pump thats worn out certainly /could/ stick and not work, but once its jostled start spinning, then continue to run til its shot off. one test for this is to have someone crank the car while you whack the fuel pump, fairly hard, with a wrench or something. if that 'fixes' it, you need a fuel pump.

wait, Regina cars only have the in-tank pump, its kinda hard to whack that one. argh, another Bosch-centric strikeout.

 

I'm gonna replace the fuel pump and see what happens. I'll let you guys know how it turns out. Thanks!

 

That pump is a little fiddly to replace. You can test it in the car to see if it runs ok under the warm start conditions. I'd not replace it w/out more proof that it's bad....

 

To test the in-tank pump, disconnect the fuel line, stick it in a jug, power the pump, and verify you get a consistent strong blast of fuel. then connect a fuel pressure gauge up (needs a volvo specific T-adapter at where the fuel line connector goes onto the fuel rail) and verify you have 42 +/- 2 PSI relative to manifold vacuum.. if thats good, and the pump isn't making awful noises, then there's no point in replacing it.

the regina pump is fairly expensive.