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Discussion Starter #1
I hate having to introduce myself to a forum with a problem, but I guess I finally have to give in and ask. My name is Steve. I've found a ton of great information here, and I thank you all for that.

Anyway, I have a '93 Classic that won't start. It cranks, it's getting spark, and it appears to be getting fuel (at times at least, the plugs have been wet).

Background, I bought it not running. I found the fuel pump fuse was blown. I replaced it, it ran, but not great. I drove it around for a weekend thinking it was bad gas, trying to run the full tank it had out of it. After replacing the fuel filter, and checking a few things we found that the alternator was spitting out spikes of AC voltage. We pulled the belt off of the alternator and it ran great. I charged it up and drove it home from the shop we were working on it at. It ran great until I pulled in my driveway. I ordered a new alternator, put it on, but now won't start.

Here are a list of things I've checked or verified:
Fuel temp sensor
Coolant temp sensor
Throttle position sensor
Neutral safety switch (it cranks)
Fuel pump and relay
Main EFI relay
EFI control unit (I have two)
Timing
It has compression (at least on a few that I have checked)
It has spark
It is getting, or has gotten fuel, as the plugs have shown a light film of fuel on them
Tried to start with starting fluid, no fire at all

Is there something am missing? That leaves the MAF, fuel pressure regulator, or injectors?? Speed sensor shouldn't matter for starting purposes. Same with the idle control I would think. I thought I've read that O2's don't either. Is there a port to check fuel pressure? I haven't been able to find one.
 

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Hi Steve,

Welcome aboard. Initial thoughts are (in no particular order):

1 - Is the spark a good, fat, blue spark? I've had similar problems when the ignition amplifier was playing up. Still gives a spark, but weak and yellow - not enough to run with. Your amp should be mounted on an aluminium plate on the inner wing, next to the coil. The aluminium plate's earthing can suffer, but a good cleanup can fix it.

2- Could you have an airleak somewhere after the airflow meter? That could weaken the mixture to the extent that it won't start, but would cause the plugs to be fouled, as you seem to suggest yours are. A very weak mixture can easily fool you into thinking you have an over-rich, flooding issue.

3 - Can you check that the injectors are definitely firing? Do you have a multimeter with pulse-width or frequency settings?

4 - I once had a very similar problem that was caused by a loose multiplug under the dash - on my right hand drive car there was a bundle of cables that went from the ecu under the driver's seat, along the side of the transmission tunnel and up under the dash. The multiplug worked loose (over 15 years!) and intermittently caused similar issues, though I can't actually remember is there was a spark or not, so probably not your problem.

Hope this helps.
 

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Discussion Starter #3
Danny, I appreciate the response. I will go through those things tonight.

Something you said made me realize I left out a piece of info. My ignition was converted over to HEI previously. I am sure that may change some things.
 

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Upon testing today, I found that I have a small capacitor that is sharing the mounting plate with the coil that is quite rusty. It connects to the coil with one small wire via the + terminal. To me it would be considered a condenser or amplifier. Is this what you are speaking of?
 

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Like Danny, i would recommend checking the basics are absolutely tickety bo before getting to involved with anything else. Especially if you have the means/knowhow to test these things, if not yell and we will advise.

Like he said, good high quality spark at the right time.

Fuel delivery at the rail and injectors firing.

Compression/cylinder pressure. I would check the other two first though.
 

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The capacitor attached to the coil is just to suppress interference. Though that does beg one big question:

I didn't know what you meant by HEI ignition so I googled it - if I understand correctly it's an all-in-one solution that incorporates the coil and distributor? If that's the case, why have you got a coil/capacitor/mounting plate etc? I'd have thought they would be redundant, or are they just sitting there doing nothing?

Anyway, regardless of that it's the quality of the spark that matters, not how it's produced, so you still need to wire up a plug out of the engine so you can see what's going on.
 

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Discussion Starter #7
The HEI is just the amplifier. Rather than spend the big bucks on virtually the same thing from Rover, the GM amplifier is much cheaper and does the same thing. I've tried two different amplifiers.

See results below.
Danny said:
Hi Steve,

Welcome aboard. Initial thoughts are (in no particular order):

1 - Is the spark a good, fat, blue spark? I've had similar problems when the ignition amplifier was playing up. Still gives a spark, but weak and yellow - not enough to run with. Your amp should be mounted on an aluminium plate on the inner wing, next to the coil. The aluminium plate's earthing can suffer, but a good cleanup can fix it. Each plug is getting equal spark, and what I would consider a healthy blue spark. Timing is set at 6 deg. advanced. I've tried to adjust it while cranking with no change. The aluminum plate has it's own ground running directly to the battery.


2- Could you have an airleak somewhere after the airflow meter? That could weaken the mixture to the extent that it won't start, but would cause the plugs to be fouled, as you seem to suggest yours are. A very weak mixture can easily fool you into thinking you have an over-rich, flooding issue. I haven't found any air leaks yet.

3 - Can you check that the injectors are definitely firing? Do you have a multimeter with pulse-width or frequency settings? I checked a couple injectors to see if they were getting a signal, and they are. I haven't gotten a chance to test every one, or have the means to test pulse width. That is on my list to do next, along with make sure they are spraying.

4 - I once had a very similar problem that was caused by a loose multiplug under the dash - on my right hand drive car there was a bundle of cables that went from the ecu under the driver's seat, along the side of the transmission tunnel and up under the dash. The multiplug worked loose (over 15 years!) and intermittently caused similar issues, though I can't actually remember is there was a spark or not, so probably not your problem. I checked the multiplugs under the dash, and disconnected them and reconnected them. No change.

Compression on all cylinders is between 155-175. Most are around 175, with just two down at 155. When the plugs were all out, I cranked with the fuel injection still powered, and you can smell that fuel is being delivered.

Hope this helps.
 

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Can you do a leak down (pressurising cylinder) test?
 

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Discussion Starter #9
A friend did a leakdown test for me and said it's good. He gave me a third opinion that the spark is plenty healthy to run the vehicle. We also manually found top dead center for cylinder #1 and verified the mark on the crank and the distributer rotor is pointing at the proper lead. We also performed a fuel pressure check. It appears the fuel pressure is fine. At first it was low, but I think it may have had air in the line. After he tried it again and pinched the return line, it has been fine ever since.

Kind of at a loss. My friend is still trying things though. Next up is to check the resistance across each injector.
 

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Discussion Starter #10
Well, it runs. I think the timing chain jumped a tooth.

We still have a check engine light, but I can't seem to get it to give me any codes. I will have to read up again on it and make sure I am doing it right.

Thanks all for the help.
 
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