Hot Start Woes: Maybe NOT Fuel Pressure?

[DMC5180]

So obviously I haven’t made a ton of progress on my hot start issue in the last few weeks. Weather in Chicago has been less than conducive to working on the car. In the meantime I’ve been researching some other stuff and reading James Espey’s Illustrated Buyer’s Guide. At the section for the Idle Mixture Adjustment Screw I noticed plug with metal hoop and didn’t recognize it. The guide says, quote, “unplugged, this is a source for a large vacuum leak.”

Ah ha! I thought maybe I’d found my problem. So I went out to the car to take a look. Where I found this:
Attachment 55953

What. The. Shit.

I guess PO thought shoving a sheet metal screw in there was somehow a good idea?! Also - a little disappointed this wasn’t caught during the inspection I had done at DMC Midwest.

I haven’t investigated any further, like by removing that beast of a screw, but I’m hoping whatever damage may have been cause by it is minimal...

It may not be what you think. The metering housing left the factory with a tamper-proof sealing plug in that hole. To remove the plug, you drill a small hole into it then thread a small screw in and pull the plug it out. Once removed you could, in theory, just stick the plug with screw back in the hole if you did not have the removable rubber plug to replace the original sealing plug. It does not take much to plug the hole. I’ve seen golf Tee’s used or even a old school lead ✏️ .

You will need too look closely at it to determine if the screw is threaded into the plug or directly into the housing. if in the housing you could have a leak around The threads. Nonetheless, it has been tampered with.


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[David T]

People use all kinds of things. On one car I found a golf tee!

[Michael]

Advance (or about any auto parts store) sells universal vacuum plugs in the "Help" section. I used one from that pack.

[DMCMW Dave]

It may not be what you think. The metering housing left the factory with a tamper-proof sealing plug in that hole. To remove the plug, you drill a small hole into it then thread a small screw in and pull the plug it out. Once removed you could, in theory, just stick the plug with screw back in the hole if you did not have the removable rubber plug to replace the original sealing plug. It does not take much to plug the hole. I’ve seen golf Tee’s used or even a old school lead ✏️ .

I've also seen that hole drilled out so big that the original or rubber plug won't fit any more. In that case, the only thing that will work is something like what you see, and such things may be better left alone as long as they are tight.

[ASquared150]

So, over the past week or so I've been able to put a good amount of time into the car. The very first thing I did was pull that screw out of the mixture adjustment screw access hole. It wasn't driven too far in but it left the top of the hole pretty marred. So until I get back out to DMCMW for the proper part, I plugged the hole with an M4 bolt that fit pretty snug and then covered it with some adhesive aluminum tape - not entirely ideal, but it should hold vacuum WAY better than the screw did.

Since I had the airbox off I also took care of my high idle - it'd been idling around 1500 RPM for a while. Long story short I adjusted the idle speed screw and microswitch screw and now it idles around 750 as it should.

And finally while adjusting the idle I noticed the car was getting way too hot - pretty quickly moving past the 220 mark on the temp gauge. Radiator fans weren't turning on. Jumped the otterstat, fans still worked. Turns out at some point the driver's side coolant pipe had started leaking at the hose junction heading up into the engine bay. So I tightened all the hose clamps I could easily reach, opened up the bleeder valve and added coolant until the overflow tank was half full and the bleeder was leaking, then replaced the radiator cap on the overflow tank with a new one. Coolant system is working properly again.

Now then, back to the hot start stuff:

After adding the coolant I took it for a quick spin to get gas (added a can of Techron as well). When I got back I let the car run until the fans had cycled 2 or 3 times and shut it down. Waited 15-20 minutes, and it started right back up and went straight to idling at 750. Very promising.

Then today I took it out again and drove around town for about 45 minutes. Got the engine plenty warm, fans cycled multiple times. Then I shut it down and set a timer for 45 minutes. Came back to the car, and it started right up again, first try. Idled a little bit rough but then smoothed out. So I drove it around a little more, let the fans cycle 2 or 3 times again, then shut it down and set a timer for 30 minutes. Again, started right up, first try.

So, is my hot start problem solved? Of all the work I did recently the only thing I can think of that would affect it would be sealing the mixture screw port off better. But even that seems like a somewhat insignifigant change to solve my hot start issue. Would adjusting the idle screw possibly make any difference? I'm worried I just happened to get lucky today on my tests and that the issue isn't actually solved...

[DMC5180]

Time will tell.

Is your Car largely stock in the relay compartment ? Meaning original fuel pump relay.


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