Friday, August 16, 2013

Fuel Pressure Sender

Next up to go on is the fuel pressure sender. This again matches my VEI fuel pressure gauge, and is an electronic sender with a 1/4" NPT thread. This sender could theoretically go anywhere in the pressure fuel line, but I think the closer to the engine the better. As luck would have it the LS3 factory fuel rail has a fitting on it, although sadly it is not 1/4" NPT. The fitting on the end of the fuel rail has a Schrader valve in it, and is presumably there to allow diagnostic fuel pressure testing by service centres. The end with the valve can be seen in the centre of this photo with the black cap on it.

The thread on this fuel rail fitting is -4AN, so we need an adapter to fit our 1/4" NPT fuel pressure sender. While a straight adapter is available, this would make it stick out a fair way, looking less than average and may also interfere with the not-yet-fitted power steering fluid reservoir. So I decided to dog-leg it, and use a -4AN / 1/4" NPT 90 degree elbow adapter together with another elbow which is 1/4" NPT on both ends, and then the sender attached to that. Here are the parts together with the thread sealer for the NPT thread.
Here is the Schrader valve fitting, remove the Schrader valve with the valve tool ($3 off ebay)
Then the fittings can be installed. The chosen method of turning it 180 degrees makes it three pieces long, but tucks it away nicely behind the injector wiring and coil pack brackets.


Friday, August 9, 2013

A few engine bolt-ons

I need to change and add a few things to the engine, and it is far easier to do most of this stuff before the engine goes in the chassis. First up is adding a water temperature sender. The factory sender is in the left-hand cylinder head, and will plug into the GM wiring harness and ECU. This factory sender is GM specific and cannot be used to feed an aftermarket gauge, but is critical to ECU operation so that the ECU knows the engine water temp. But the gauge I am using of course needs its own sender. The left and right cylinder head castings on Chev LS engines are the same alloy casting, so the location for the factory sender is also in the right-hand cylinder head and is blocked with a threaded bung from the factory. This is the best place to house the aftermarket water temp sender.

The gauges I am using are from VEI Systems and they came with the water temp sender. Like most aftermarket senders the thread is 1/8 NPT. The thread in the cylinder head is M12x1.5, so we need an adapter. Autometer make such an adapter, part number AU2277, but the internal diameter of it is just slightly to small to fit the sender, so I drilled it out by about 1.5mm

Then the body would fit inside the I.D.
And sadly this is where it all went wrong. Drilling out the I..D by 1.5mm weakened things enough that the housing of the thread adapter cracked upon tightening in the head - I didn't do it that tight I promise! I felt it give when tightening, and thankfully stopped quick enough that I was able to back it out with snapping it off in the hole, and without damaging the head. The crack can be seen in this picture just below the end of the thread.
Time for Plan B. I bought another thread adapter, and Autometer also make a "shorty" temp sender which fits natively in the adapter (part number 2259). I am not using Autometer gauges, thus I could not be sure that the resistance from the VEI sender and the Autometer sender would be the same, so I had to test it. So I cracked out the water temp gauge, a 12v battery, and for each sender I ran it under the hot water kitchen tap for a few mins and monitored the temp reported on the gauge - this confirmed that both senders are sending the same resistance to the gauge. In this pic it is measuring the VEI sender and the Autometer sender can be seen on the bench. Both senders reported the same temperature on the gauge

So the shorty sender went in the thread adapter with a bit of thread sealer and it's all buttoned up ready for attaching the sender wire.