Hot start/heat soak problem - this seems to help

[Zed Head]

After absorbing all of the ideas on where the heat soak problem originates, I decided to try the most direct solution I could fabricate and blow air directly on to the injector bodies. I have a ZX fuel system blower fan and ductwork from a ZX motor I had bought in the past but didn't want to use the bulky ductwork or the thermal switch (which doesn't seem to be effective on the ZX's anyway). So I bought a bathroom fan timer from Home Depot to control the fan (one hour range), and went to the wrecking yard and scavenged two 18" pieces of pre-heat tubing from a couple of 80s-90s Chevy S10 exhaust systems ($3). Taped the two pieces of tubing together, cut 6 holes in it over the injectors with an X-Acto knife, blocked one end and taped the other to the elbow from the ZX ducting which fits the blower nozzle, and mounted everything in the engine bay. The new ducting sits nicely under the fuel rail. It's made for the high heat environment of an exhaust system so should be fine. I zip-tied the blower to the condenser for my AC system, and the timer to my steering column. Considering its overall ugliness, it all fit in pretty well, even the timer on the steering column, and is mounted solidly. The pre-heat tubing will take a bend and hold it without collapsing. I used metal foil ductwork tape (Nashua 324A) on the tubing. There are probably better ways to do it, but I was in prototype mode.

I've had it in for about two weeks and not had a single hot-start problem. But today I went in to Office Depot, after a fairly long drive down the freeway (hot engine and it's close to 60 degrees here today), and when I came out I realized that I was in the dreaded 10-30 minute zone and had forgotten to turn the blower on. I started the engine and had one of the worst heat soak problems I've had all winter. The engine chugged along on what felt like 2-3 cylinders for a good 1-3 minutes, which felt like 10-20. It finally settled down enough to leave. I went down the block to another store went in for about 15 minutes but remembered to turn the blower on, came out and it started right up like it was cold.

Just passing this along for anyone that wants to try it. The air coming out of the holes shoots forward so mount them behind each injector to get good air flow on the injector body. I would take a picture but my engine bay is not meant for looking. I'll post a few links to parts instead.

I'm trying to find a dependable automatic timer relay that will turn the blower on when the ignition is turn off but haven't found a good one yet.

http://www.amazon.com/Standard-Motor-Products-Pre-Heater-Hose/dp/B000C7UPQU/ref=wl_it_dp_o_pC_S_nC?ie=UTF8&colid=30R38L6H5WA0Q&coliid=I2PEPLP3OQMVN8

GE In-Wall Spring Wound Countdown Timer-15304 at The Home Depot

Edited March 16, 2013 by Zed Head

[FastWoman]

Very cool! (Ok, bad play on words...)

So does the ZX fan duct that wraps over the top of the valve cover not fit under a Z hood? Or maybe you weren't able to find one?

[Zed Head]

I wanted to get cooling of the fuel rail out of the picture. Isolating variables. There are only four air streams (four of the injectors are paired up) pointed directly at the injector bodies, underneath the rail.

Plus the ZX mounting scheme, with the blower bolted to the side of the engine and the ductwork over the valve cover, is bulky and difficult to work around. In this setup the blower is off of the engine and the cooling tube can be slipped off and removed easily. It just lays on top of the engine under the fuel rail. The only attachment point is the slip fit on the blower nozzle.

It's an experiment cobbled together from available parts.

[black gold man]

I mounted that timer on the side of my center counsel with just the little knob showing.

[black gold man]

lot more CFM than the zx blower the way you made the duct you could use this blower.

Jabsco DC (12V) 150 CFM Flexmount 3' Blower - 36740-0000

Or more CFM First Choice Marine - Blowers

Edited March 16, 2013 by black gold man

[Zed Head]

How does the ZX do with the use of a timer? Better than the thermal switch?

Thanks for those links. I followed the second to Walmart - Find the Attwood Turbo 3000 Blower at Walmart.com. Save money. Live better. Fits my budget better. Looks like it might be okay mounted on the firewall.

Summer project.

[black gold man]

"How does the ZX do with the use of a timer? Better than the thermal switch?"

That is in my 78.

[Willoughby Z]

This is very interesting. How long did you set the timer?

[black gold man]

!5 min

[Willoughby Z]

!5 min

I'm surprised that 5 minutes would be enough. But with a high CFM fan...

A perfect world for me, would be to have a circuit with a relay that starts an adjustable timer relay when the ignition turns off. That way, I wouldn't have to remember to set the timer. Maybe an override/kill switch for frequent stops or interrupting the "fan on" cycle after a quick stop.

Just some thoughts...

BTW, thanks, Zed, for sharing this.

Edited March 21, 2013 by Willoughby Z

[Zed Head]

I think he might have meant 15 minutes. I have a one hour timer and just turn the knob about 1/3, so 20 minutes. If it's still running when I come back I just let it blow while I drive. I have a fuel pump cutoff under the dash also that I always flip anyway, not because my car is worth stealing but because I think it's probably easy to steal.

Saab apparently had a delayed-off relay on a few of their models to run an electric fan but they started failing closed so they recommended replacing them with regular relays (I think that have a thermal switch in the circuit also). There are solid-state electronic timers out there but I haven't found one that stays closed for over 5 minutes and/or will run on 12 volts.

[Willoughby Z]

... There are solid-state electronic timers out there but I haven't found one that stays closed for over 5 minutes and/or will run on 12 volts.

Part Number E1220- Timed Off 20 minutes/ 9-30v