# can I add in a primer?



## luckyvision (May 24, 2007)

I have an echo 400B backpack blower i'm fixing up. it was neglected, full of varnish, missing the air cleaner etc.

I fabed in a cone paper filter for a techumsa/sears.

I replaced the carb (wa-55) fuel & pulse hose. (pulse port is clear)

it runs great but is impossable to start cold without a shot of carb cleaner to prime it (full choke, full throttle)

*my question: *
can I add a primer inline to the carbs? i have a spot for it, can fab a bracket etc. worry is where does the pressure go when i prime it? I can't pull it out the end of the carb, only the inlet side. don't want to stress out the needle or diaphram...

Thanks, --Lucky


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## 30yearTech (Sep 14, 2006)

I would say no, there is no way to add an inline primer. The type of primers you see on the newer blowers are not really primers, but rather a purge type system, that only charges the carburetor with fuel, but does not prime the engine to start. If it runs good once started, then I would look at the choke and it must not be closing off enough to deliver the extra fuel needed for cold starts.


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## luckyvision (May 24, 2007)

*Don't ever tell me i can't do something, lol*

your right 30 year, there is no _conventional_ way to add a primer, so i took a different route... 

a little background: i'm working on an echo PB300 (or 400? i forget, it's in the shed) backpack blower. the carb was hopelessly gummed up. replaced the carb with a new one & the only problem was that it wouldn't self prime to start. a single shot of carb cleaner was all it takes to get it to fire & run, then it runs great.

the owner reminded me that i worked on it last year, but he left gas in it all fall & winter. also last year i said the compression was low (i had forgotten this, & didn't check it this time because it runs so good it didn't occure to me... i rechecked & got about 65 psi :/ )

so, to the point: i created a primer port by drilling thru an 8/32 screw to use in place of the fuel pump cover screw. there is a lock nut halfway down the screw so that it acts like the head of the original screw, holding the cover on. 

a second fuel line with filter was plumbed from the tank to the screw (head cut off) with a primer inline.

works like a charm, starts on the second pull cold every time! 

how did i drill a hole straight thru an 8/32 screw?   i'm just that good, lol


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## 30yearTech (Sep 14, 2006)

Your a machinist, right??

Does this setup inject fuel directly into the throat of the carburetor?


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## luckyvision (May 24, 2007)

30yearTech said:


> Your a machinist, right?? *Nope*
> Does this setup inject fuel directly into the throat of the carburetor? * yup *


nope not a machinist, just someone who has always taken the term "Yankee Ingenuity" to heart. it's just how i think.. 

i looked at it and said "how can i get fuel into the carb to prime it, & can it be done "elegantly"? (i prefer not to have a job look 'rigged')

I knew i would be using a self contained primer unit (the snap in type) and a second line into the tank with a filter.
one option was to take a small brass tube & plumb it into the aircleaner housing at an angle & try to aim it past the closed choke lever.. didn't love that idea..

then i thought, if i can somehow replace that pump screw with a fitting, that'd work just fine. but i had to make it hold the cover on well too.

Since the cover screw is 8/32 thread, i drilled a 1/4" hole in a scrap of 1/2" plywood, sandwiched a 1" 8/32 Cap screw in the wood with fender washers & a nut. i chose the cap screw because it would be easier to center up the drill bit.

i centered the 'jig' on the drill press table over the hole in the table, & secured the jig with a couple of spring clamps.

i chucked up a #47 wire drill bit & drilled the hole very slowly with plenty of machine oil & stopping frequently to blow out the chips & drop fresh oil on it. took almost 15 min to drill it all the way thru, but the patience paid off. the hole was almost perfectly centered.

i then took the screw off the jig, worked a plain nut & then a nylon locknut on the screw. the end with the head was going on first, so the threads had to be good after i cut the head off, so thats what the plain nut was for, to sraighten out the threads after cutting the head off. i set the lock nut the same length as the original screw threads.

installed the new 'fitting', made a bracket for the primer & plumbed it all in.

nope, never been a machinist, all self taught ... lol

--Lucky


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