sf4018

Thanks so much @sitous and @JohnCh for the pointers, I managed to get her running again and save the weekend. 🍻

You were on the right track, it’s a loose wire on the pump relay. I jiggle the relay around and I can hear it click and the pump goes on. Same if I wiggle the wires behind it. Just gotta figure out how to fix it in the field.

Another track day, another breakdown. All was good on track then fuel pump cut suddenly. Fuel pump has no electrical power, inertia switch is ok but has no power either, so it’s upstream of that. Fuses are all ok. ECU is bypassed so it’s not that. Everything else is functioning normally. Anyone have any ideas?

Dunno if you're still looking, but I'll be at COTA on Halloween weekend in the 420R SV (with lowered floors), you're welcome to stop by and jump in.

Exciting times, congrats on a great build!

Those are 4mm or 5/32” on mine

Should be Fastener Pack ZBC02. It doesn't give sizes on the pack sheet I have except for the rivet - 1/8" x 0.39". Nothing for the buttons and sockets.

Did the first ECU setup run with Steve of SBD Motorsports yesterday. A few relevant notes: 1. The ECU fuel pump run command signal can be programmed to run as long as the engine is turning over, which is safer than the "always on" mode that it's wired as right now (currently only killed by key turn out of position 2 or inertia switch trip). So electrically it would have been better to keep the fuel pump control relay and harness intact. I will re-install a new harness over the winter, but for the tracks days coming up next month it's gonna be fine. 2. Steve tuned the cold start perfectly, it fires up first time now. Awesome. 3. Idle and low speed tuning took several hours and apparently is the hardest part of the tune. He made some changes while I was driving around the neighborhood with the PC connected to the ECU with a desktop session to the UK via cell. It was really cool to see how even small changes to mapping can make a noticeable difference. If I can figure out how to tune it myself later on it'll be car nerd heaven.

SBD Motorsports recommended replacing the stock lambda sensor with an Innovate LC-2 Wideband System, so I went with that. Mechanically it swaps out easily without modification. Electrically this is the plan… The only unknown is whether the signal 0V NB8 should be grounded (probably to the chassis). Looking at the Caterham schematics the NB8 signal ground wire is shared with several other sensors, plus it’s close to 0 ohms to battery ground already, so right now I’m going to lean not connecting it. Ground loops are not good.

Has anyone replaced a standard lambda sensor with a wideband one? I believe it's 6 wires but there's only 4 on the current sensor connector (brown/blue/black/white).

I believe so, I can pull up the raw O2 sensor value and lambda number on the ECU software, I’ll be able to send this to the Aim Solo2 for recording. Life is good with an unlocked ECU 🙂 Edit: Upon research it looks likely that it’s not a wideband lambda sensor, so I’m gonna replace it.

I only see 1 throttle body at the entrance to the manifold, everything past that seems static, but I don’t really know. That’s good info thanks! So I started up the engine cold a few times now, it reliably holds idle either the first or second attempt, so I don’t think it’s a temperature thing, maybe air bubbles in the line working it’s way out. Whatever the reason, it’s pretty good now. SBD Motorsport have been great so far, it’s so great to be able to send any data I want to the AIM system. They responded about the RPM meter not showing RPM correctly they said it was a setting for 4 pulses per cycle instead of 1, I’ll try that tonight. Just gotta do fine tuning after that. What a painful project, but the end result turned out pretty good. I appreciate all the help and support from everyone, it made a big difference! Thanks! Simon

I blipped the throttle to keep the engine going for a while, then after it warmed up some it held idle fine. I also experimented with the 2 electrical control variations for the pump. Here’s how the original on demand pump controlled by the ECU and pump control relay (same as original internal pump control) works… …the pump runs for a second to charge the pressure, then I start the engine, fails to hold idle, then the pump is re-activated by the ECU. How it ever worked before i don’t know. Fuel pressure was around 30psi. I know the plumbing isn’t setup for on demand but I wanted to see what happened. So the relay is now chopped off and ECU signals taped off. Next was running the pump full time by wiring YG154 and B10 to the pump… …holds about 52psi. Engine was cold, even with this higher pressure idle didn’t hold. So the electrical is sorted now. I’m gonna let the engine cool completely and see if it’s a cold start issue. If it is, which looks likely, I guess I’ll need help what to change in the ECU.

Moving on to the new ECU…it’s so nice to be able to go in and configure stuff. The RPM meter on the dash doesn’t work properly, it’s like it’s showing pressure or something, but I’ll figure that out later. The main issue right now is the engine doesn’t idle, anyone have a clue what could be the problem? Here’s a vid of the problem… https://youtube.com/shorts/u2HwIthDE-g?feature=share

Does sound electrical, hopefully something simple and obvious like a loose ground wire.

It was plumbed in by Caterham, there’s a handle on the dash. So I put 5 gallons in, set off the pump for a second but no gas flow or pressure. Maybe I have to put more fuel in or bleed it somehow?

Plumbing finished, may fine tune later. Just gotta wire up the pump now.

Great video and excellent driving!

The new ECU is in, started the plumbing, starting at the engine and going back. 5/16” fuel line quick connect connector, 6AN hose clamp, 7.9mm stainless braided high temp fuel hose… Although the internet said to use hose clamps not cable ties for fuel lines I used the latter like the original installation, seems fine to use for the tunnel… For the exit point from the tunnel above the LSD I didn’t feel comfortable snaking around the hose like the old one because it’s quite a bit larger diameter and didn’t want to risk pinching it, so I cut a notch in the wood above the LSD to use as an exit point. It’s cut to the right a little to make room for the fire extinguisher on the left…

317mm from the top to the lowered floor. Note that it’s not straight down, there is a ridge at the lowered floor section at least for mine.

If the temp bumpers are expensive I would just go a scrapyard get some comically large bumpers like F150 for $20. They won’t be able to deny it just cos it looks stupid.

Bumpers are so hard to mount reliably.

I'll be headed that way for a visit in the next few months. If it gets out of pre-order status we'll figure something out.

Best chance of cool air I would guess would be running a duct to the side of the radiator, it would have to be closable if it rains though.

Some issues with the copper pipe that Caterham sent… 1. The rear exit looks fine except the connector goes back down which is odd… …it’s not the end of the world but will mean some hassle finding the right elbow/banjo connector to bring it back up and keep it away from everything else going on down below. Seems awkward. 2. Using this pipe means 4 connection points instead of 2. 3. Even though it’s installed in a pretty well protected area it would seem rational to want to put a protective cover over it. The old line was a crappy hard plastic tube with a shroud. I’m leaning towards using stainless braided flexible 7.9mm tube that will run directly from the tank t connector to the engine rail. Easy install and only 2 connection points. The tube is rated to 250F so should take the heat, and the braid should protect the tube from stuff hitting it. I checked the cover of the old fuel line and other than dust it’s in immaculate condition so I don’t believe there’s a particular risk damage from stuff flying around from the road.