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First post - car turns over but won't start

3K views 5 replies 3 participants last post by  Roundabout 
#1 ·
First of all I would like to introduce myself, I'm Andy. This is my first post and I'm writing because I couldn't find a solid solution in the forums. I have a 2007 Elise with a BOE rev310 supercharger, surge tank, catch cans and some other stuff.

The problem I currently am having is my car will turn over but won't start. Last time I drove my car I heard a loud whining coming from the engine compartment which I'm pretty sure was the fuel pump in the surge tank. A couple of days later I went to start my car and it would turn over but not start and sometimes backfires while trying to start.

I've checked the common problems:
-All fuses in engine compartment
-Alarm/immobiliser
-Inertia switch was tripped and reset
-I took the opportunity to upgrade both fuel pumps with Aeromotive 340's, that was fun
-Fuel pressure is good
-I have spark on all cylinders
-Inspected fuel injectors, no clogged injectors
-Checked fuel injector input voltages with multimeter set to AC and saw movement when trying to start
- Has new lightweight battery
-Battery light is on when running. I haven't troubleshot this yet
-I have O2 CEL and p0171 system lean
- Cleaned maf sensor
-Cleaned air filter
-I have not done a complete vacuum leak check yet. No obvious air sounds in engine compartment

It seems like I have should have spark, fuel and air. I'm not sure what to check next. Any help would be much appreciated.
 
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#2 · (Edited)
If it turns but doesn't start, do you smell the unburnt gas? If not, I would think fuel issue. Can you tell if the fuel injectors are actually firing? Sometimes you can put a screwdriver handle to your ear and then touch the tip to the injector and it will amplify the sound. You've checked voltage to the injectors but maybe the ECU signals are not getting through?

Have you done any work recently or had any other repairs/issues? Maybe check ground wires, see if something has rattled loose? A compression check is easy to do and can rule a lot of things out.
 
#3 ·
If you're sure that the injectors are firing, then there should be a strong smell of fuel from the exhaust. If you have checked the spark by pulling the plug and grounding it out (the plug should be wet as well). As long as there's no reason to suspect compression then move on. The injectors won't fire without the crank trigger signal. You should just double check that the cam sensor connection is sound. Some cars will fire with only the crank sensor, but I think most OBDII systems would check for the cam phasing as well.
 
#4 ·
I smell no fuel and spark plugs are dry. I checked voltage at the injector connector and see 0vdc. I believe one leg of the injector should always be at batt voltage. I've checked some of the grounding and have had no issues. The cam sensor checked out ok. I'm struggling to get to the crank sensor and have not been able to text it yet. The connector is in a really bad spot.

Here's some more history of my car. I bought it in early 2016 and it drove amazingly. Previous owner put about 8k track miles on the car. All mods to car were done by previous owner.

After some time I noticed the car was lacking power. I initially checked the air filter but only checked one side and it was the wrong side lol. I later cleaned the maf sensor. Replaced spark plugs and coils. 3 of the spark plugs were really worn and had a gap of about 1.3 mm. I later correctly checked the air filter again. It had so much dirt on it I'm not sure how it got any air. Cleaned the filter and the car has more power again. With hard acceleration the car stumble.

The car had a p0171 code that I cleared after the car wouldn't start. The inertia switch was tripped and I reset that. I don't know how long it has been tripped for. So the car has been running on the surge tank fuel pump for awhile.
 
#5 · (Edited)
Not smelling gas, plugs are dry, P0171 (lean fuel) code... Fuel system is definitely looking suspicious, but someone smarter than me may know of a reason that something would cause the ECU etc to not fire the injectors... They may be wired and "working" but not getting instructions to fire? Something like that kind of happened to me previously.

I think you are supposed to see voltage at the injector at all times when the key is turned to on, then one of the wires is used to get a signal from the ECU that tells the injector to fire. In my case I once had a misfire (running on 3 cylinders) due to an injector not firing. I had voltage at all injectors (I think), ended up that I felt lucky that mine was resolved by simply re-seating the ECU and wiring harness connectors.

I'm a bit surprised there was not a misfire code... It sounds like the stumble at hard acceleration may have been misfire, or worse... detonation.

If it was running too lean and put under significant load, detonating is a possibility, and if there was damage from that then you may have some compression loss. A compression test is pretty quick and easy, would you mind trying one and posting up the results for each cylinder? You can usually "rent" a compression tester for free from Autozone or O'Reillys, etc. The 11.5:1 stock ratio means the pressure should be higher than most cars, all 4 cylinder readings should be within 15 psi or so of each other, in the 190-210 psi range if I remember correct. It would be good to rule this out for sure, but I think you might be OK on this front because even if you lost compression completely on one cylinder it should still start and run on 3 cylinders.
 
#6 ·
Usually no fuel = immobilizer is active.
How did you check the immobilizer?
If you pull the driver's seat and the rear panel, you can jumper the immobilizer just to make sure that is not the issue.

Fuel will also not be injected if the crank sensor isn't pulsing. You can check that while cranking use your OBD2 data logger (Torque and a OBDII dongle, bluetooth for android wifi for apples)
 
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