Thought I would start a new thread on troubleshooting the no-start condition on my "new" 745ti from this thread viewtopic.php?f=5&t=1713 Here are some of the ideas carried over from the original thread.



I checked the CPS and it appears to have just been changed, looks new and was tight in the housing. No change after re-installing.



Pulled the dist. cap and rotor, both look fairly new as well. No oil in the housing. If the seals were leaking there would be oil in the housing right?

Have been reading through the FAQ's on Brickboard and Swedishbricks, would the Radio Suppression and Fuel Injection relay's be next on the list to check? I pulled a Fuel Relay the last time I was at PNP, it has a fairly new date on it (1998) so it might be worth popping in? Also the fuel pump sounds good each time, I crawled under and took a quick look at it. the P.O. said it was changed (looks like a rebuild) as well as the ECU so we should be safe eliminating those two items.

Just to re-cap this is a no-start condition all of the time. To get it started required grounding out an injector which was not a sure thing to get it started. Once running it tried to stall every time I hit an intersection on the way home, however under load on the highway it ran fine.

Crazy idea, check the grounds, make sure they aren't all corroded out to poop. Also...maybe make sure you have the right injectors in the veh or maybe pull the rail and injectors out of the intake manifold and check that they are spraying nice and even. Check for air leaks in the intake system and just maybe double check the wiring, maybe a connector is unplugged (try to pull them off, I had an evap on on but not plugged in and stumped me for a bit) or maybe a connector is not connected to the right thing?

Personally I would check the injectors first, maybe even before that just make sure the distro cap and rotor, spark plugs, and wires are in good shape.

I'll go through the grounds and check, I have checked the dist., rotor, wires, plugs all look fairly new (changed by the shop that was working on the car recently) although I haven't pulled any of the plugs. Not too sure how to go about pulling the injectors, or what I should see when i do. Will also go around and check all of the connectors I can find. I did notice one plug under the intake manifold that's not connected to anything, I assumed (I hate that word) it was a test port? I'll snap a pic and post it up to let you have a look. Oh just so you know what you're dealing with, this is all a first for me so if it seems like I don't know what I'm doing...

Grounds...you're on the right track as far as I'm concerned. Get it sorted one ground at a time.

it sounds like a bad ground or an ECU.
we did a 740 yesterday and harness on the block was rubbed thru.

Start with the basics. Is the no start condition caused by no fuel , no spark, or both? Then start trace the circuit that related to that system. If you just start replacing parts (probably with used ones) you will never know if you are curing the problem or making it worst.

Yes there are some very common problems including:

Radio suppresion relay
Fuel pump relay
CPS (although new what is the wiring like and the flywheel clearance)
grounds
ignition amplifier (does the 2.4 use these? was a problem on 2.2)
ignition switch

just to name a few, but please start with a plan or you will just get frustrated.

What Ian said.

Get yourself a noid light set. Great $6 dolla purchase in my case. Plug it in and see that the injectors light. I use and abuse my fluke meter like no other.

The extra 2-pin bosch connector under the intake sort of near the idle motor is an unused diagnostic thing on LH2.4 7/9 cars, though IIRC, cars with the cold start injector don't have it...no idea. I don't know what plugs into it and don't really care...everything you need to diagnose an LH2.4 car is right there.

Radio suppression relay is an easy one...can be swapped with the aux cooling fan relay on the coolant bottle that seldom fails (same relay) (the A/C doesn't usually work for long enough in a volvo to give that thing a workout )

If it has spark, the crank position sensor works fine. You want to make sure there is good hot spark. If the fuel pumps prime when you first turn the key, the fuel pump relay likely works 100% fine, though the ECU that triggers it once the engine spins might or might not work....earlier #560 and 561 and 563 non-white label ECUs are notorious for burning out the fuel pump relay trigger ground circuit at best when they go...though turbo cars are less afflicted that 89-late 90 LH 240s...great way to get a late 245 for 300 bux tho. If the car won't even sputter, the fuel pump relay circuit being bad in the ECU is unlikely...if the fuel pumps prime that is.

Check the grounds on the intake, at the driver headlight and by the ECU...all can in one way or another cause a no-start. Check the alt ground, ground at the head and negative battery cable while you are at it for wear...less of an issue in a 7 than a 240T.

Check your cam timing...always an easy one on an unknown engine and often missed.

Pull off the fuel return line on the fuel pressure regulator and check for nice smooth flow, and pull the feed if you aren't sure or put a pressure gauge on it. Pull the vac line and make sure there is no gas in it. Veryify when it is running that the idle speed changes with vac applied and removed from the pressure regulator on the rail.

LH2.4 cars do use the ignition power-stage thing by the driver headlight. It doesn't go out very often in them...they got di-electric grease on the connector and much better thermal paste between the heat-sink and the module (what causes the early ones to flake out and finally die).

Ignition switch in a 7 series....ugggghhhhh.....I can change a blower motor in a 240 faster than one of those. Heater core in a 760 makes it a parts car to me now...unless someone is willing to really fork over some dough (I hate 760s and like them as recycled metal anyway). I'm sure in your climate you get to do more ignition switches...fun...the tell tale sign in a 7 that the ignition switch is about to shit out on you is if the headlights don't quite come right back on after you start the car (or rather return the key from "crank" to "on") and that the wipers either don't work (unless you jiggle the key) or do weird stuff like cycling to park once at random or with another electrical bit...fun...early 700 cabin electronics...we can only hope those cars stay off the road for people like me that dislike electrics....though they do look like god's gift to electronics compared to a series 3 jag and land rover of comparable year.


On a 90 740, I start with the spark and cam timing and then go on to all the heap of reasons why on earth it might not get fuel. Make sure you pull the plugs and check they are clean and ok. Also, check the resistance of the coolant temp sensor at the ECU plug...you will have a devil of a time getting an Lh2.4 car started (it will...eventually....it takes a LOT of cranking and gradual fuel/throttle feathering) with a bad CLT temp or one that is disconnected. Do make sure the thing has compression or sounds ok too...took me a while to figure out a blown HG on one.

Stragely, I can diagnose no-starts and running issues way faster on K-jet, SU or weber carbs than EFI. Clearly...electrics are not for me. I just have a big bin of them and lots of little test tricks. I still have to go through everything and if there is a wiring issue, it will take me for freaking ever to find it. I must be sick in the head.

My old 91 had a random no-start. It would go months without a problem, then all of a sudden it would not start. I'd leave it over night, and in the morning it would fire right up as if nothing had happened.

Anyways, earlier in its life I had changed the RPM sensor because the original was broken at the block. I got the 29 dollar one from FCP. Anyways, after a year of this random problem a guy at work gave me a Volvo RPM sensor to try out. No problems since. I sold the car, and they guy driving it still hasn't had a no start problem.

Your problem sounds more serious than that though.

Basics fuel, spark, compression. Then go from there. I know grounds are an issue. I have had 2 other things (on friends car) go and that was a bad ground on the intake mani (dads car), and the Coolant Temp sensor (James' car).

Car throwing any codes?

Jordan

Thanks to everyone for all of the suggestions so far, I finally have something new to report. I went through the following grounds and sanded, cleaned and reinstalled using OxGuard (conductive paste):

- 2 ground straps on the valve cover
- the FI grounds under the intake mani
- main chassis ground
- both chassis grounds beside each headlight
- main ground at the ECU
- main battery ground
- ground below the ABS unit

I checked for spark and it's good, as before the fuel pump kicks in when the key is turned on. The noid light did NOT light up so no FI pulses. The ECU is a 563 (the not so good one?) and was recently changed by the previous owner as was the fuel pump which always cycles and it sounds good.

I got the mtce. file from the PO which only had 1 WO from all of the work that was done recently. It noted that the car was brought in for a no-start "again" (I think all of the ECU, fuel pump, plugs, wires etc. had been done previously), cranks over but will not fire. They changed the CPS but also stated they suspected a short in the FI wiring harness. They then ran another wire from the ECU to the injector harness and restarted numerous times. There are no other WO's after this job. I checked for codes and there are none, probably due to having the battery disconnected while I was messing around. I also swapped the A/C and Radio Sup relays.

If the rebuilt ECU was at fault it wouldn't fire the fuel relay right? If the CPS was bad I wouldn't have spark? I have checked and cleaned all of the grounds. Not sure where to go next?

You're getting there.

There are 3 or 4 grounds under the dashboard, but if you've got the ECU ground that would be the major suspect.

You're sure you're getting power at the injectors during cranking? The ECU grounds the injectors but the noid light wouldn't light if there's ground and no power.

The ECU wouldn't necessarily be considered "good" just because it runs the fuel pumps. It just means it's working, but the output to the injectors (a fairly beefy transistor) might not be. Throw your noid light across +12 and the injector ground at the ECU plug and see what happens (pull the cover off the plug and plug the plug into the ECU, test from the back side). Try pulling one injector plug off at a time and repeat this test - maybe you've got a dead short injector causing the ECU to not fire the injectors.

Having said all this, since the car will continue to run once it's running, I would think the problem is not in the ECU or injectors. I seem to recall, though, that you're having trouble keeping it running at a stoplight, so maybe it's having trouble opening the injectors at low pulsewidths. Could still be a weak +12v at the resistor packs. Make sure you check this voltage while you're trying to crank, with all 4 injectors plugged in.

Ignition switches can do funny things: For instance, the switch can run the starter but forget to run anything else while in the "start" position, and work fine otherwise. I've had this happen to me more than once. Make sure you've got good power to the ECU and to everything else while you're cranking. This includes the injector +12 and resistor pack.

Just some ideas, mostly focusing around one thing. Have a look and report back, Jim.

Matt

No, I need to check for 12v. Using a meter would I pull an injector harness and stick the pos lead in the harness and neg to ground, then measure voltage while cranking? Sorry, but I've never used a meter before so I'm trying to troubleshoot and learn all at the same time.



Sorry you really lost me here.



I'll need to do some reading up on this as well...



Thanks for all of your help Matt, I need to do some reading to try and understand what you are talking about. If you have a "For Dummies" version that would be great, this is starting to make a bit of sense to me just going to be slow going.

When you're checking the harness you can backprobe the connectors, meaning put the multimeter in the back of the connector

So leave it connected and just pull up the boot and go in the pos side of the plug?

You can do it like that, or do it like Andy suggested and like you guessed: pull the boot back and probe the connector from the wire side. In this case, you've got three other injectors hooked up to this load so pulling one off isn't going to change things much, but if you have something sensitive like a coolant temperature sensor you can't always just unplug it to test for things because you'll screw up the test by removing the sensor.



What I started out saying is that your ECU has many parts - some run the fuel pump and some run the injectors. Don't judge the ECU as "good" just because the fuel pumps work. That only means that the ECU is getting power, recognizing RPM, and is able to run the fuel pumps. It might not be able to switch on and off the transistor that grounds the injectors.

The next idea was to test the injector circuit at the ECU plug, checking for a break in the harness. It's probably not necessary, though, because your car WILL run - just not while your starter is engaged. That's why I keep coming back to the ignition switch. Why it dies at intersections, though... that might be another issue.

Finally, I was thinking that maybe ONE of your injectors was bad, and that by pulling one plug off an injector at a time (i.e., trying to run the car on 3 injectors) it might suddenly spring to life. A simpler test would be to unplug each injector and probe the terminals in the injector itself - you should see 1.5-2.5 ohms in each, I believe. 0 ohms would indicate a dead short, infinite ohms means it's wide open. Neither of which are good.



The resistor pack is behind the driver's headlight, right above the battery. It's a little cluster of white tube-looking things with wires sticking out of it. There's a plug at one end that plugs into the engine harness. One wire feeds all 4 resistors, and then out the other end of each resistor runs a wire that individually goes to the plug (then to each injector, then to the ECU). Test for +12v at the common feed wire while you're cranking, with all 4 injectors plugged in. If you can actually get the engine started (starting fluid, grounding an injector, whatever you need to do) test for +12v at the common feed again and see what it's reading. Note that if you test on the other side of the resistor (one of the individual wires ultimately going to the injectors) you'll get +12v with the ignition key "on" but the car not running, and pulsing MUCH lower (+2v or so) with the car actually running.



Let me start over:

Because your car is not firing the injectors while cranking (evidenced by no action from the noid light) you've got one of two possibilities: either your ECU is not grounding the injectors, or your injectors are getting no power. Since this is only happening during cranking, I'm mostly suspicious of the ignition switch. To be honest, I'm not 100% sure where the resistor pack gets it's power from: the ignition switch or the ECU (which gets it's power from the ignition switch).

So test #1 in my mind is to make sure the ECU is actually getting power while cranking. Since the ignition control unit is separate from the fuel control unit (two different locations in the car) you can't judge the ECU operation by the presence of spark. Pull apart the big plug connecting the ECU to the wiring harness and plug everything back together. Find the +12v wire (I don't know which one this is, sorry - consult your wiring diagram) and make sure it gets power when you turn your key "on". Try cranking and verify that the ECU has power during cranking. Yes = continue, no = change ignition switch.

Test #2 is to go to your resistor pack. This is located right behind the driver's side headlight, just above the battery. It's a bundle of 4 white cylindrical resistors, 5 green wires, and a plug. One of the wires in that plug goes to one end of all 4 resistors - this is the main feed wire. The other end of each resistor has a wire that comes back to the plug, which ultimately ends up passing through the injectors and gets grounded by the ECU to turn on the injectors. Test the voltage at the main feed wire & make sure it's +12v with the key "on", and it should be the same with the key cranking, give or take.

Test #3 is to pull the plugs off all 4 injectors and probe the injectors themselves - across the two prongs in the injector you should see 1.5-2.5 ohms of resistance. Any more or any less and you should be changing your injectors.

If you're interested, the resistor pack is there because your ECU can only switch about 5 amps of current, so your 4 injectors need to draw 1 amp or less each. Therefore the overall resistance of the circuit has to be about 13-14 ohms. In the '80s, an injector big enough to run turbo-4 engines tended to be low impedance, meaning that the internal resistance of the injector is only 1.5-2.5 ohms. Rather than have 4 larger transistors to handle the current, the Bosch LH-jetronic system only had 1 transistor so Volvo had to add resistors to the injector circuit to reduce the current.

The idea of the day was that the low impedance injector would pass loads of current, opening the pintle much faster for better accuracy. Then the ECU would quickly switch the transistors on and off at just a high enough value to keep the injector open, and then when the ECU opened the circuit, the injector would quickly shut off. High impedance injectors take longer to open and take longer to close, so can be less accurate at really low and really high duty cycles (%open time as the engine is running), but because they were typically smaller they tended not to run at really low duty cycles anyway. Nowadays the injectors are so much lighter and faster acting that you can get double the flowrate without having to go low impedance, and you can get injectors 3-4 times larger than you used to be able to get.

Edit - Hopefully we'll have time to have a look at your car when I'm down there. I'm still bringing some stuff down there for you next weekend (May 23) so maybe we can look at it then.

IT'S ALIVE!!!!!

I have been reading as many threads on tbrix, brickboard, s'bricks as possible looking for a similar scenario to my problem and found this post on BB http://www.brickboard.com/RWD/?id=1257022&rss=1 where it was suggested to jumper the RSR plug to eliminate the RSR as a problem. I had already swapped the A/C relay without any luck when it dawned on me that the pre-purchase inspection report stated there was no A/C... both relays are pooched!!! I jumpered the 2 big wires as instructed in the thread and VROOM, it RUNS!!!!! The bad RSR probably explains the stalling problem when it was running???

Mucho thanks to everyone, especially Matt for your in depth explanation of the ignition system which has been printed and is going in to my Volvo repair bible. To say this made my day would be the understatement of all time, I AM STOKED!!!!

Now my next question is where can I find a relay FAST??