Fuel starve in left or right corners?

[KnifeySpoony]

In my duratec powered 420r, I Believe the fuel pump pickup is on the left side of the tank. However from all my googling I'm only reading about people getting fuel starve in right handers (maybe those are different setups?) Today at Laguna, twice in turn 2 (long left hander after downhill long hard braking zone) with about a third of a tank (can never tell with these gauges, but was only the second session after a fillup), I got a very brief but severe hesitation. No popping, which I've heard in other cars during fuel starve. No issues elsewhere on track. Otherwise, car flawless all day. 

 

Could this be starvation or should I be looking for other causes? I've always  run two 20min sessions on a tank without issues, but maybe burning more fuel today from pushing harder with sticky tires. (New set of A24 ZZR, PR day)

[Pokey]

Wild shot in the dark, but you might check to make sure your crank sensor hasn't started backing out.

[KnifeySpoony]

Interesting, someone else mentioned a possible sensor issue too. I will have a look over the sensors. Aren't they clipped in though?

[wdb]

Is there a low oil pressure shutoff?

[KnifeySpoony]

Not that I'm aware of. And I'm on a dry sump so that seems unlikely. I will review my video though monitor the oil pressure gauge.

[Pokey]

7 hours ago, KnifeySpoony said:

Interesting, someone else mentioned a possible sensor issue too. I will have a look over the sensors. Aren't they clipped in though?

 

Yes to having a spring clip holding the connector to the sensor, but the sensor itself can start to work itself out.  A lack of signal from the crank will cut the ignition and, at least in my car, the fuel.  For me the problem arose on the track in fast corners.  If that isn't it then I would consider manipulating the harness with the car idling to see if you can trigger a stall.

[KnifeySpoony]

Sensor is clipped in securely but I will fiddle with it. 

[Pokey]

32 minutes ago, KnifeySpoony said:

Sensor is clipped in securely but I will fiddle with it. 

 

But is the sensor itself in there nice and tight, or has it backed out a bit?

Edited May 26 by Pokey

[KnifeySpoony]

Hmm it felt secure (ie no wiggle to it), but i could see well to see if it had backed out of the engine itself. I think i saw a couple screws holding it in... Just nip them up? 

[Pokey]

Might just be one screw, can't recall, but, yes, make sure it is secure.

[Pokey]

Assuming that isn't the solution, I'd try moving the harness around while idling, particularly the connectors that lead to the injectors and the coils.  Different car and different symptom, but I chased random and intermittent stumbling that was caused by a bad pin in one of those connectors.

[KnifeySpoony]

Starve was much worse at Sonoma this weekend. Could only run 7 laps on a full tank before starve would happen in T6 (long left) on the 8th lap. This behavior was consistent all weekend. I am on new stickier tires and carrying much more speed through there, but it seems odd that I could previously run 2 whole sessions, now can't even get through one full session. I'm looking into solutions to help the fuel pump pickup get to lower down or more central in the tank. Trying to avoid a more complex surge pot setup with secondary pump, return line, etc. 

[11Budlite]

I'm not sure how you could modify the stock FP pickup to get it lower and moved to the center, if your FP is like the one in my Sigma-powered car. My pump looks something like this:

 

You might consider modifying the assy to something like what John did on his car. Check out pg 3 and 4 of his build thread here: 

 

Edited June 2 by 11Budlite

[KnifeySpoony]

OK, i'm pretty sure the baffle in the tank has failed. I can hear something rattling around in the tank. New project awaits. Any chance of repairing a baffle in situ, or this just means new tank is going in?

[Croc]

My experience with Caterham tanks is that there is no baffle.  Every one I have ever owned is a big open single cavity.

 

You have an in-tank pump.  I think something has fallen or broken off it.   Pull it out and have a look.  No fuel pickup modifications should be needed if the unit works correctly.  Pull it out from the top and have a look inside the tank. Its a reasonable sized opening to look into - use a spark safe light of course.  

 

The pump unit can be sourced cheaper than with Caterham - use the marked code to search at Rimmer Bros in the UK.

 

[IamScotticus]

I was experiencing cut-off on sharp rights in my DCOE shallow wet sump electric pump Xflow.  I didn't get it resolved before I stopped driving.  Thought it might be bowl level flooding, starving, or oil pressure.  The turns were so brief, like low speed into a driveway, I ruled out the tank.  Sure, I could be sucking air, but, at those speeds, surely the pump would have refilled the line?

These 7s....always something 

Edited June 30 by IamScotticus

[Kitcat]

My ‘97 Caterham’s x-flow would go about 5K miles before the engine mounts were shot. So on hard turns at track speeds the engine would shift. This would cause the intake stacks to press against the cutout in the bonnet (hood). That would cause an air leak in the intake system. That would cause sputtering that would resolve as soon as the curve ended.

 

Only took about a year to diagnose:). I think forum member BBall came up with this diagnosis in the course of chasing a corner sputter in his X-Flow.

 

All in the FWIW category.

Edited June 30 by Kitcat

[sf4018]

On 6/1/2025 at 7:37 PM, KnifeySpoony said:

I am on new stickier tires

Do tell

 

[IamScotticus]

On 6/30/2025 at 11:35 AM, Kitcat said:

My ‘97 Caterham’s x-flow would go about 5K miles before the engine mounts were shot. So on hard turns at track speeds the engine would shift. This would cause the intake stacks to press against the cutout in the bonnet (hood). That would cause an air leak in the intake system. That would cause sputtering that would resolve as soon as the curve ended.

 

Only took about a year to diagnose:). I think forum member BBall came up with this diagnosis in the course of chasing a corner sputter in his X-Flow.

 

All in the FWIW category.

I actually considered that as a possibility but thought no way in hell period. thanks for confirming it.

[KnifeySpoony]

Pulled the fuel pump. Indeed there is no baffle that I can see. The float arm and completely detached from the pump and was loose in the tank - that's what was rattling around. I don't think I mentioned but the fuel gauge never reading full was another symptom that appeared on the last day I drove the care. My working theory was that the mythical detached baffle was preventing the float from rising fully... Anyway,  I reattached it and put the pump back in. So back to square on the fuel starve. I suppose it could just be a product of more lateral grip. I also wonder if the pump could be slowly failing?

 

 

Also related; how does one disconnect this fuel line? I struggled with it for a while, then just left it connected when I pulled the pump.