84 240 DL (LH Jetronic 2.0) cranks, but won't start. I do have spark.
As background info, the LH ECU and the wiring info were replaced about five years ago.

Thinking fuel pump issue, I replaced both pumps. No help. The new pumps do not come on when I turn the key, although I can get them to come on using a jumper wire in the fuse box.

I also replaced both fuel pump relays, and all fuses relating to the fuel system. Still nothing.

A noid light test does not flash when the car is cranking.

Following Bentley's advice, I tested for battery voltage at the fuel pump relay's terminals, and get voltage at terminal 30, but none at terminal 86. Bentley's says, "If there is no voltage, locate and repair the wiring faults using the appropriate wiring diagram."

That's where I get lost. Where is the logical place to look for wiring faults, given my symptoms?

 

Were you checking for voltage with the key on? The three things that feed voltage on that wire are the terminal block next to the battery, the ignition switch, and fuse #12.

 

Bentley's says, "With the ignition OFF, check for battery voltage at terminals 30 and 86." That's how I checked it.

 

It's a typo, check for voltage with the key on.

 

Thanks for your help. Looking at your diagram, that makes sense. I checked with the key on, and there's plenty of voltage at terminal 86. But it still doesn't start.

 

To check the system relay (and what controls it), look for battery voltage on the orange wire connected to the air mass meter during cranking.

To check if the ECU is grounding the fuel pump relay, look for voltage on one of the yellow/red wires that connect to a injector while cranking.

I would also inspect any replacement wires going to the ECU, and clean the ECU connector.

 

I peeled back the rubber hood on the air mass meter connector, and with the connector plugged in, and while cranking, checked for and found voltage on the orange wire.

I did the same on one of the injector connector's yellow/red wire. Found voltage.

Also, checked wires at the ECU (both the ECU connector and the wires are all relatively new), and cleaned the connector.

Still no luck.

 

It's a long shot but you could try starting the car with the air mass meter unplugged. Otherwise my guess is the fuel ECU is bad - it's not grounding (opening) the injectors. The biggest hint to this is the noid light not flashing.

The other thing to check is to make sure you are getting ignition pulses on ECU pin #1 (grey). Bentley says you should see "some" voltage on that pin during cranking.

 

Well, now I am embarrassed. I re-tested with the noid light, and this time it did flash. The prongs were so close together on the light, that they did not fit well into the injector connector, so I bent each one outwards a bit and plugged it in. It flashed on all injector connectors (although I think I needed to test only one). Still, the plugs do not appear wet after cranking. I'm not sure what that means.

The car still did not start with the air mass meter unplugged.

So, I'm not sure where that leaves me. New fuel pumps, new relays, new fuel filter, injectors receiving a signal. Wiring in good shape. ECU relatively new (although that doesn't mean it works necessarily). I have a spare ECU which I think is functional, and I connected it, and that did not help.

Before the car stopped starting, it would start every time, but was idling very rough - surging, etc. I repaired all of the potential vacuum leaks I could find.

Could this be a fuel pressure regulator problem?

 

You might want to make sure you are getting fuel to the rail while cranking. Yes, the pressure regulator is a possibility, the timing is way off (belt problem), or bad compression.

 

Long shot, but have you peeked in the oil filler hole on the valve cover while someone cranks the car to make certain the cam is moving? If it isn't your cam belt has broken.

 

Lots of times these are caused by a bad reluctor or hall effect sensor. I'm not sure what LH 2.0 has. I would guess that it uses a hall effect sensor in the distributor. Those things just die after so much use. In LH2.2 cars if it dies no signal is given to run the rest of the car, ie. fuel pumps, spark and such. If it's never been replaced, it will only save you a head ache down the road when it goes. It seems common for them to go arond 200k mi and 20 years.

 

He has spark.

 

Thanks, guys. I do appreciate the input.
To swiftjustice44: the belt is intact.
To Titan Joe and bubba240: I do have spark, which I think indicates that the Hall sensor is working. Correct?

To bubba240: I will check to see that I have fuel to the fuel rail when cranking. I do know that when I replaced the fuel filter, gas spewed everywhere when I disconnected the fuel line, so there is some amount of pressure there. As for the timing being way off, is there some way to adjust timing without the engine running?

Again, though, I don't hear the fuel pump when I turn the ignition on, nor do I feel any sort of vibration from the pump. To me that suggests an electrical issue (but you guys have knowledge way beyond mine).

Would a bad ignition switch cause these problems? Could I possibly have a bad ignition switch, even if it cranks and I get a positive noid light test?

 

Is it a yellow weak spark or a good blueish white spark? Mine would lame spark when the hall effect sensor was bad a few times and it threw me off. If it's good, then yeah I'd throw that idea out.

 

Getting fuel at the rail (disconnect the line and put it in a bucket) during cranking will rule out the possibility of the line being obstructed, the pump being wired backwards, and verify the electrical path to the main pump is working. My LH2.2 car does not prime the pumps when turning the key on. But you did see voltage on the Y/R wire during cranking so they should be getting voltage.

Diagnosing a lack of fuel pressure/bad regulator is a pain because you have to use a banjo fitting for the gauge between where the hose and the rail connect. Usually they fail by leaking gas into the vacuum line cause a very rich condition.

Have you tried starting the car with the fuse jumper wire in place (pumps constantly running)? I ask because the ECU will turn the pumps off if it doesn't see the ignition pulses on pin #1 (safety feature).

As suggested I would make sure the spark is strong and the wire order is correct. I would then put a timing light on it during cranking to check the timing.

If everything is still looking OK I would do a compression test.

 

yeah I know it's been a long time, but I am having what looks to be the very same problem, with my '83 244 LH2.0
Did you ever figure out what the problem was?