engine hard to start when hot

[Jack2048]

Hello All,

I have a 1994 5.0 FI 8 cylinder VP engine.

When cold starts easily.

After running for a while and engine is hot, when I try to restart, I have to give full throttle for it to turn over.
When the weather is cooler, say in the fall, this is not a problem.

A typical scenario is would be like yesterday I launched ran for about 20 minutes. Stopped the engine and hung out for a other twenty, and had problems when I went to restart. Happens all the time.

Engine works great while running.

Engine has new plugs, new water pump impeller, new fuel pumps, new filters among other things.

Ideas?

 

[alldodge]

If the motor has a carb then the motor is getting to much gas. First thing to look at is after its hot and shut down look at the carb. See if you can see fuel dripping down the throat of the carb. See if the choke is fully open. If you see any fuel then carb needs cleaning and adjusting

 

[Jack2048]

Thanks but, it's Fuel Injected.

 

[tlewis1]

I would still suspect it is getting to much fuel or fuel is leaking while it is sitting as AllDodge mentioned. Possibly a leaky injector or injectors?

 

[Jack2048]

Ok, maybe the injectors are leaking.

That would account for the hard start when hot and the rough idle.

But I don't have this problem when it is cooler out. Or is that just an anomaly?

I can pull them and do a static test.

I have already replaced the o-rings on the injectors. I found some re-manufactured injectors on eBay for $80 / four.

 

[alldodge]

OK, so FI is fuel injecte.
If high pressure fuel pump is putting out to much pressure it can cause issues. When cold the engine needs more gas because the fuel does not atomize as well, and there is not (in most cases) time for all the fuel pressure to come up to max.

If the MAP sensor still things its cold it will give it more fuel. More fuel in a hot motor makes things worst.

What do the plugs look like?

What model 5.0 is it?

Suggest not throwing parts at it until some diagnostics can be done further.

 

[Jack2048]

>If high pressure fuel pump is putting out to much pressure it can cause issues.

Pump is new Volvo Penta pump.

>When cold the engine needs more gas because the fuel does not atomize as well, and there is not (in most cases) time for all the fuel pressure to come up to max.

Yes, I was reminded of this when I flooded a two stroke hedge trimmer the other day... that was a nice ten minute upper body work-out

>If the MAP sensor still things its cold it will give it more fuel. More fuel in a hot motor makes things worst.

I will figure out how to test and check it hopefully tomorrow.

>What do the plugs look like?

New, but I can pull one and look.

>What model 5.0 is it?

1994 5.0L FI PMDA V8. Volvo Penta.

Is that what you are looking for?


>Suggest not throwing parts at it until some diagnostics can be done further.

Agreed. A bad sensor would make more sense than injectors. And now that I am thinking about it, I remember a while ago checking the resting pressure and it was good. But it should be re-checked.

 

[alldodge]

Thanks for supplying the info. As a non-VP guy I'm trying to find the motor online, so far have been unsuccessful at finding it. Don't know if its a MPI or TBI

Maybe Scott Danforth or Fun Times or muc can assist because It don't want to send you down a road that may not be correct

 

[Jack2048]

Just Google volvo penta parts, go to their store. And you can look up all the schematics. 1994 charcoal engine 5.0 fi pmda

Here is a link
The forum won't let me add the link and I have to go to Costco now. Will add it when I come back k

 

[Fun Times]

Just so we all know, This engine model is a MFI (Ford engine)....They tend to be bit harder to diagnose as far as lack of technological access via scan tools go compared to technology of today.

Some basics to ask would be, is the front flame arrestor cover screen clean, how about the throttle body? What did the old spark plugs look like when you removed them? Fuel fouled at all?

Could be an engine temperature sensor issue. Would have to try and find a sensor resistance values chart to test the sensors both hot and cold to compare notes.

Boatinfo has a manual online that covers the MFI Ford Diagnostics you'll want to start reading as it may help you out some.

 

[Scott Danforth]

Not a lot of support for the Ford based motors

 

[Jack2048]

lack of technological access via scan tools go compared to technology of today.

The joys of owning tech from 1994.

Some basics to ask would be, is the front flame arrestor cover screen clean

Yes

, how about the throttle body?

Yes

What did the old spark plugs look like when you removed them? Fuel fouled at all?

I don't rightly remember.

Could be an engine temperature sensor issue.

The gauge indicating temp sensor works correctly, but I don't know if that is the same signal going to the computer.

Would have to try and find a sensor resistance values chart to test the sensors both hot and cold to compare notes.
Boatinfo has a manual online that covers the MFI Ford Diagnostics you'll want to start reading as it may help you out some.

I do have the factory Seloc manual for the engine.

 

[Fun Times]

I'm not quite sure if there is one or two temp sending units on this engine as I haven't noticed it mentioned yet in the parts diagram and it's been a long while since I've had my hands on one to work with but todays engines do use two temp sensors. One for the gauge and one for the ECM....That mentioned, there are two intriguing components name wise that might be of interest to look further into either in your manual or the one online at boatinfo for the symptoms you seem to be having.

They are item numbers 34 and 51 http://www.volvopentastore.com/Engin...view_id.782702

34	Terminal, Choke

51	Connector, Air Charge Edit: 31 and 52 mention temp cooling. Item number 26 is your Valve, Throttle Air Bypass that might be affected, http://www.volvopentastore.com/Upper...view_id.782709

 

[Jack2048]

I'm not quite sure if there is one or two temp sending units on this engine

I think there is only one, have never come across two.

your manual or the one online at boatinfo for the symptoms you seem to be having.

My physical manual does not cover this area.
Can you please provide a link? I am not seeing where to click on the boatinfo.no website. I am a developer by trade and well, let's just say I am having trouble navigating the page. I can get the widgets to scroll, but the text description below is off screen and I can't figure out which one is pertinent to me.

Terminal, Choke

? I guess the online manual will explain?

Connector, Air Charge

Don't know what this is.
Item number 26 is your Valve, Throttle Air Bypass that might be affected,

They are item numbers 34 and 51 http://www.volvopentastore.com/Engin...view_id.782702

I can rip that apart and clean it.

 

[Fun Times]

I'm not sure yet if the manual will help explain much of the above I mentioned thus far...I sort of just now opened up the manual to start having a look around for you.

To get the manuals to read where you need them, use Control - and + to zoom in and out the main home page...It will allow you to see the wordings below so you can navigate better.

I'll go against our policy of posting direct links to boatinfo for you to help.....Though we're (iboats) trying to get away from having to....Long story behind the why.

In here you can arrow through the pages,
http://boatinfo.no/lib/volvo/manuals...rd_mfi.html#/0
http://boatinfo.no/lib/volvo/manuals...d_mfi.html#/12

Item # 26 is your Idle Air Control Valve. It might be cleanable...Just be careful till you see how it works on this engine should it be different.

Edit: This/these page/s talks about the air charge and resistance values for the sensors, http://boatinfo.no/lib/volvo/manuals...d_mfi.html#/62

If interested to know for diagnostic tools for this engine, search online and EBay Volvo penta breakout box.
http://boatinfo.no/lib/volvo/manuals/hu-ford_mfi.html#/4

 

[Scott Danforth]

I do have the factory Seloc manual for the engine.

Seloc manuals are knee pads and are NOT factory manuals. Seloc manuals are not worth the paper they are printed on

get a set of factory manuals for your MD series Ford (yes, its about 1000 pages of manuals)

you can get them here http://www.volvopenta.com/volvopent...lication_search/Pages/publication_search.aspx

you can view the manuals here:
Electrical http://boatinfo.no/lib/volvo/manuals/md_elect.html#/0
Engine http://boatinfo.no/lib/volvo/manuals/md_engine.html#/0
Fuel http://boatinfo.no/lib/volvo/manuals/md_fuel.html#/0
EFI for Ford Engines http://boatinfo.no/lib/volvo/manuals/md-ford_efi.html#/0

here is the diagnostic chart for hard start - long crank http://boatinfo.no/lib/volvo/manuals/md-ford_efi.html#/10

 

[BRICH1260]

Are you sure that it is fuel injected. A`94 year engine is a very early year. I didn't think Volvo started injecting until early 2000`s.

 

[Jack2048]

Are you sure that it is fuel injected. A`94 year engine is a very early year. I didn't think Volvo started injecting until early 2000`s.

Yes. I am really sure.

I have:

• Cleaned fuel tank
• Cleaned fuel rails
• Replaced fuel filter
• Replaced fuel pumps - different story
• Pulled and cleaned the injectors (wow, what a difference in spray pattern!)
• Pulled the heads and had them milled
• New pistons and rings.
• more, can't remember the rest.

So, yes, I know that it is injected.


Scott Danforth & Fun Times, thanks for the info. I have some work to do and may not be able to get to it until tomorrow, Wednesday. So, you may not hear back until then!

 

[Jack2048]

The rail pressure on the fuel rail lost 2 1/2 psi over ten minutes. Holding at 30 an hour later.

Seloc manuals are knee pads and are NOT factory manuals. Seloc manuals are not worth the paper they are printed on
you can view the manuals here

Ok point made, I have been browsing the online manuals. Much more info. Thanks for the resource, How I hate Flash, but that's off topic.

Throttle Air Bypass

FunTimes, I pulled this. Not sure how to test this. The sensor reads 10.7 ohms. But did not change reading when I ran a hair drier over it. Only went down to 9.8 Ohms after ten minutes in the freezer.




Someone asked about spark plug condition this was taken right after I temporarily started the engine for the pressure test:



That's all for today.

 

[alldodge]

This is the Idle Air Control (IAC) valve

Fuel pressure seems good but the one plug looks like a bit of oil and is really wet looking maybe from gas. What kind of plug is the TR55?