Cold start up & stall - 4.3Gi

Technologic80 · **Posted:** Wed Jun 05, 2013 9:50 am

Ive always had a fickle port engine, it would crank and crank for a long time before it fired. Sometimes it would start up at that point, or stall and unless you crack the throttle a little, it would have trouble starting.

Twin 4.3Gi's (Throttle body fuel injected).

Now this year my starboard engine is doing this thing at idle where it tries to stall, then the engine shoots up the RPM's a few hundred to compensate. Yesterday, it stalled for the first time ever at idle.

Last year I did full tune ups on both engines - plugs, wires, cap & rotor. I replaced the fuel/water separators last spring so Im going to do that today (its time.). The spark arrestors are both clean. Last year I replaced the low pressure fuel pump on the port engine too.

This sucks, I could live before the with port engine being a crab but now the starboard too!?!

Any suggestions where to start troubleshooting?

Bliss36 · **Posted:** Wed Jun 05, 2013 10:08 am

Quote:

or stall and unless you crack the throttle a little, it would have trouble starting.

Clean the carbon off the pintle of your IAC motors on the throttle body's and throttle blades. Sounds like it's having trouble getting the correct amount of air flow on start up. Since it's not a typical closed loop fuel injection style control system it probably bases your IAC control steps off of set parameter's that are changed due to carbon build up. It's a good place to start anyway?

Technologic80 · **Posted:** Wed Jun 05, 2013 2:51 pm

Bliss36 wrote:

Quote:

or stall and unless you crack the throttle a little, it would have trouble starting.

Clean the carbon off the pintle of your IAC motors on the throttle body's and throttle blades. Sounds like it's having trouble getting the correct amount of air flow on start up. Since it's not a typical closed loop fuel injection style control system it probably bases your IAC control steps off of set parameter's that are changed due to carbon build up. It's a good place to start anyway?

You just reminded me... last year I replaced the IAC "just because" and the old one was pretty carboned up. Im going to go out and take the spark arrestors off and the IAC's and clean the throttle bodies with carb cleaner. Will report back.

ric · **Posted:** Wed Jun 05, 2013 2:55 pm

I would see about having the injectors cleaned.

Winter Sux · **Posted:** Wed Jun 05, 2013 4:05 pm

A very common problem in TBI 4.3's is the base gasket on the TBI unit. It "can" cause the issues you have but very simple to check. Open the throttle wide open and with a light, look inside the bore. If you can see any of the gasket protruding, it's toast. They're cheap and easy to change. It's worth having a look.

John :mrgreen:

Technologic80 · **Posted:** Wed Jun 05, 2013 8:54 pm

Winter Sux wrote:

A very common problem in TBI 4.3's is the base gasket on the TBI unit. It "can" cause the issues you have but very simple to check. Open the throttle wide open and with a light, look inside the bore. If you can see any of the gasket protruding, it's toast. They're cheap and easy to change. It's worth having a look.

John :mrgreen:

GOOD to know. I will check that. Thanks for the tip.

ric wrote:

I would see about having the injectors cleaned.

You think that has something to do with it?

Today I also changed my water separator/fuel filters. Last year I used Sierra brand, this year I have genuine Volvo Penta parts. They are two totally different filters. :shock:

The Sierra were a little larger. I also noticed the volvo penta fuel filter has a seal on the inside of the fuel filter that mates around the threaded pipe that comes out of the fuel filter/water separator assembly; the Sierra did not. Dont know if that has anything to do with anything or not...

I should add when the engines are warm or if they have been run in the last 12 hours, they have absolutely no problem starting or idling. It only does this when cold. Last year I replaced both coolant temperature sensors. No change. No codes are being recorded either, I've jumpered it and used the LED at the data link connector.

ric · **Posted:** Wed Jun 05, 2013 10:05 pm

My buddies fuel pump went on his 4.3. Injectors were crudded up

Winter Sux · **Posted:** Thu Jun 06, 2013 3:54 pm

Don't be so quick to have your injectors cleaned. TBI is quite reliable. If they do need a cleaning, they can be cleaned without even removing them. There's a simple way to check that type injector. Get a timing light and hook it up, with engine running, point the light at the injector stream. The timing light will freeze the fuel pattern coming from the injector to the naked eye. You should see a uniform spray in a cone shape. Bring the RPM up and as it increases you will hear and see the band pulse width change. The pattern will have the cone altered slightly from the higher volume of air entering the engine but if the fuel spray cone pattern remains good with no large drops of fuel being injected, then leave well enough alone. If they do need to be cleaned, find a local tech that can clean them on the engine. With my cleaning kit, I simply remove both fuel lines from the TBI unit, block them with tools in the kit and pull thhe fuel pump fuse. Plug the return port, again with kit tools, then hook up the regulator and a can of cleaner to the fuel inlet on the TBI, set it to 11 PSI, fire it up till the can of cleaner empties, reassemble the lines and all and she's done. I charge 100 bux per engine for this service.

I support the idea of the IAC as well. When cleaning this, also be sure to clean the passage that it breathes from. A simple pipe cleaner usually does the trick, followed with some carb cleaner. Keep us posted.

John :mrgreen:

Technologic80 · **Posted:** Fri Jun 07, 2013 8:50 am

I never thought about cleaning the IAC passage - can I remove the IAC and simply spray throttle body cleaner where it was?

Also, I noticed my stbd side low pressure fuel pump is now pretty noisy. This is how the port side went down last year. I had to replace it because I didnt want to be left stranded when the fuel pump finally sh*t the bed. Looks like that *might* be the cause of my new problems on the stbd engine at least.

Im going to buy some more TBI cleaner today on my lunch hour since I ran out the other day and clean the IAC passage tonight.

Technologic80 · **Posted:** Mon Jun 10, 2013 7:07 am

Cleaned the IAC passageway over the weekend, no change

What do you guys think about the fuel pressure regulator having gone bad? Or the vapor separating tank at the back of the engine? Just a few things I've read on the web.... not sure how often those parts go bad though and I dont want to throw parts at it $$$

Recap: my port engine will crank excessively with a no start condition only when cold. When the engine is warm, it starts right up like the day it left the showroom floor. But if you wait longer than 12 hours and go to start it, it might take 5 minutes to get it fired. Starboard engine - no problem, starts up no problem.

Is is hard to swap the fuel pressure regulators? Maybe I could put the port engines regulator on the stbd engine and see if acts up over there??

Btw my TBI unit looks just like this one:

ric · **Posted:** Mon Jun 10, 2013 7:50 am

Did you do a compression test?

Technologic80 · **Posted:** Mon Jun 10, 2013 8:25 am

ric wrote:

Did you do a compression test?

When I bought it last spring, I had a mechanical survey performed and although I don't have the numbers with me right now, everything was well within specs. The engine was hard to start since the day I bought it.

At first, I just figured it needed a tune up, but I did that and its getting worse.

Bliss36 · **Posted:** Mon Jun 10, 2013 8:55 am

Quote:

Also, I noticed my stbd side low pressure fuel pump is now pretty noisy. This is how the port side went down last year. I had to replace it because I didnt want to be left stranded when the fuel pump finally sh*t the bed. Looks like that *might* be the cause of my new problems on the stbd engine at least.

Might be time for a fuel pressure test. If you cycle the key a handful of times to cycle the fuel pump before starting it, does it start easier that way?

Technologic80 · **Posted:** Mon Jun 10, 2013 9:39 am

Bliss36 wrote:

Might be time for a fuel pressure test. If you cycle the key a handful of times to cycle the fuel pump before starting it, does it start easier that way?

No, not at all. Which baffles me even more.

I should take a video of the behavior and post it. I can turn the key 3-4 times before starting it and hear the fuel pump prime each time, makes no difference.

Bliss36 · **Posted:** Tue Jun 11, 2013 7:40 am

If you can take video maybe get both engines on cold start with a close up of the throttle bore while doing this:

Quote:

Get a timing light and hook it up, with engine running, point the light at the injector stream. The timing light will freeze the fuel pattern coming from the injector to the naked eye. You should see a uniform spray in a cone shape. Bring the RPM up and as it increases you will hear and see the band pulse width change

The timing light trick does give you a perfect view of the injector spray. Also I really think a pressure test is in order, especially if the pump is getting noisy.

Option B: Get 2 base gaskets and swap throttle bodies and see if the problem goes to the other engine. Easy to do and it will isolate your problem. It will also rule out this common problem from winter sux:

Quote:

A very common problem in TBI 4.3's is the base gasket on the TBI unit.

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Cold start up & stall - 4.3Gi

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