Cranks but no start, no prime -- 2008 LGT Auto, Wagon

[birkhoff]

 

RESOLUTION: The fuel pump relay under the dash was bad. See diagnostics and pictures in post #5 & 6 below. 

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Couldn't find much about this via site search.  

Car is a 2008 LGT wagon, auto, 180K km (canadian car) that has some worrying noises coming from a RocketRally built engine. Decided to open up the timing area and check the tensioner, idlers and WP just in case it was something simple.  When I went to start the car with the timing covers  off it cranks but will not start.   No sound at all from fuel pump when ignition is on to sweep dials so priming/run seem disabled. 

Diagnosis so far:

Both fuses good. 

Fuel pump relay clicks when gauge sweep initiated. 

Refit the Alt/PS belt in case the ECM uses the ALT signal for something. No change. 

Found  no fuel at engine quick connect so confirmed no prime pressure -- not just that it is an unusually quiet pump. 

Hard wired pump to 12V and it primes and  engine will start and run as long as I keep 12V at the pump. 

Digging into the manual it looks like this car has a fuel pump controller, not just using the ECM for this.  To be honest, I'm working from a 2005 LGT manual, but this seems true for all 2.5 turbos. If there is something different for 2008?  That would be good to know. 

The car has some minor rodent damage to the wiring in the engine area. No damage behind dash or inside car. No exposed wires found yet, but I can only see what I can see without tearing too much apart.   This could be a confounding issue, though there were no other oddball behaviours prior to taking the front off the engine. 

The obvious clue is that I only messed with the front end of the engine prior to this happening. Drained coolant, removed rad and fans, pulled off aux belts and crank pulley; removed timing covers and then . . . no start/prime.   I'm sure I've run one of these engines without coolant and covers for a test like this before and not encountered this problem. 

Temporarily out of ideas,  I plan to check voltages and grounds at the controller.  Where is it located in this US spec Wagon?  Wiring diagram WI indicates it is somewhere rear-ish on the driver's side but where?

Any other pointers or ideas welcome.

 

 

Edited April 2 by birkhoff
Found the problem

[birkhoff]

The controller is bolted to the body stiffener at the left (driver) rear above the rear end of the wheel well.  Unfortunately you have to take the entire side trim panel off to get to it.   Disconnecting the module from the loom, I get about 12 V at the power-in lead  (RB) when the key is on. It does not cut off after the dial sweep for prime, so that must be managed by the controller. 

Probing the ground line (B) from the controller confirms a good ground.   

The rest of the voltage measurements are confusing, so I'll do some more investigating before speculating how this works.  After plugging and unplugging the controller, the pump still doesn't prime when the gauges sweep.

Image 1 below shows rear side of left rear wheel well with controller hiding up behind. Image two with  D-pillar ground and controller hanging.  Image 3 is the layout of connector block.  RedBlack should be Bat V with key on,  Black is ground. Green/Yellow and Green/Red go to the pump.  Light Green and Light Green/Red are to ECM. 

Edited April 2 by birkhoff
Photos added.

[KZJonny]

Apologies for not being able to help with the diagnosis, but if you suspect that the fuel pump controller is bad, tho I have a hard time imagining why that might be the case, then replacement with the MY06 STi and similar design is recommended, it is similar in all regards, but flows more volts to the pump.

Also, if you so much as suspect rodent damage, I would consider pulling up all the carpets etc... I had a *tiny* bit of mouse damage on my car one year, and only discovered it when doing the fuel pump. It was all underneath the rear seats + insulation etc...

 

If all that fails, maybe check cam and crank position sensors + wiring? I am pretty sure the engine will crank but not start if those are not working correctly. (Fuel is clearly the problem here, but other things maybe at play as well?)

[birkhoff]

Thanks KZJ.  I'm gonna keep the engine sensors at the bottom of the list because it runs normally when I jump the pump. That still leaves the possibility that some disagreement between the sensors and ECM are messing up the controller signal, but not an outright component failure.   That said, early in diagnosis I replaced the crank position sensor 'cause I had a good one handy and it was easy to swap out,  but nothing changed. 

I agree that failure of the controller  at exactly the same time as my work on the engine seems far fetched. I need to carefully review what I touched in the engine and trace backwards to see if I messed up a wire or ground somewhere.  Failing that, I'll put the front of engine back together and see if by some miracle it runs.  It is missing one ground strap (RHS -- the left is intact) which I need to attend to anyway. 

 

[birkhoff]

Diagnostics (used the fuel pump wiring diagram from page WI-78 from the 2005 FSM attached)

1. Pulled the glove box trim and confirmed a 'click' from the fuel pump relay.  There are three relays in there, so used a stethoscope to make sure the fuel pump one was clicking. 

2. Check voltage on Bat + terminal at fuel pump:  1.4 - 1-8V during dial sweep.  Not enough to start the pump.

3. Hard wiring the pump terminals to an external battery the pump works and the car starts, but dies as soon as power removed.  Pump good.

4. Uncovered the Fuel Pump Controller (FPC) on the driver's side rear. This is a pain in the wagon as all the side trim rear of the back seats needs to be removed. Back probed the terminal block at the FPC. With key ON and Battery at 12.5 V:

Heavy input wire RB (T10) 1.5 -1.8 V+ variable  0V with key off. 

G/R pump wire (T6)  1.5-1.8V + variable.  0V with key off. 

G/Y pump wire (T5)  didn't record. 

Lg control wire (T9) 5V+ for a few seconds on dial sweep

LgR control (T8) didn't record. 

B ground wire (T5) confirmed 0 ohm to ground. 

The low readings on T10 Bat + and T6 are suspicious. 

5. Pulled off connector from FPC and checked voltage again.  

T10 Bat + was now 10.5 - 11.5 V+ variable 

T6 Pump positive now 0V.  

The inconsistent voltage at Bat+ and pump positive is the main symptom, as is the very low voltage when connected to the FPC. Suspect the relay is not closing properly and/or adding high resistance to the circuit.  Getting to that relay requires more disassembly up front.  Dang it!

WI Wiring Sys_fuel_pump.pdf

[birkhoff]

A few days later and about an hour of trim removal time . . . . 

Replaced the fuel pump relay and everything works as normal.  Great. 

Reader might wonder why we didn't deal with the relay diagnostics first?  It is a big job to get in there.  Centre console, console trim, more lower dash parts all have to come out. Even then, there is no way to back probe the assembly and even getting the relay in and out is a challenge due to access behind the wiring looms.  The voltage showing at the FPC Bat + is probably the correct value for back probing the lead wire out of the relay, after all. Not easy to do, but easier than getting to the back of the relay cluster under the dash. 

Opening up the old relay the contact points were definitely charred.  This car has been off the road for a couple years. It is only started to move it around and sometimes the battery is not the best. So this may have been the reason the relay burned, and yet another reason not to try to run these cars with a marginal battery. 

Edited April 2 by birkhoff

[KZJonny]

Sounds like the perfect time to install the Deutschwerks (or take your pick of brands... or make your own...) heavy duty fuel pump wiring + relay kit.

It deletes the factory location (annoying!) relay and provides a high quality Bosch relay in it's place, plus 10 gauge wiring all the way from the battery to the pump.

Since it still uses the stock fuel controller, you still have pump voltage stepping, and are not running at 100% pump all the time, but you will get better voltage to the pump without it going through all the 12/14 gauge wiring it normally does.....