captbuddy
Veteran Member
My 1978 Prairie 29 with 4-108 is getting hard to start. Any ideas why. It has always started right up.
Hard to start
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CharlieO.
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Filters, air leaking into fuel systems, lift pump going bad, low compression, weak batteries.
captbuddy
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Thanks Charlie
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That is where I would srart.
SteveK
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What did you do on the engine since it last started quickly?
Have you changed fuel filters for instance?
Have you changed fuel filters for instance?
captbuddy
Veteran Member
No. Nothing has changed. When I do get it started and run it for a few minutes then I switch it off. And then it starts right up. I’m I Pensacola fl with the temperature in the 40’s. But was trying to start it in the 60’s temperature. I don’t think these Perkins diesels have a pre-heat switch. At least mine has never had it.
Check it for blowby, a related condition of low compression, by removing the oil filler cap while running at idle and putting your hand over the nozzle about 4-6” away. If you feel heavy pulses, that is heavy blow by. Light pulses are ok and none is great.
Heavy blow by means that the pistons and/or rings are shot.
You can skimp along for a while with an engine heater. A warm engine turns over faster while cranking and lets the diesel fire off quicker.
Do you have lots of smoke after starting? If it drops off after the engine warms that means that the rings are going bad but not shot. Continuing smoke is another indication of shot rings.
David
Heavy blow by means that the pistons and/or rings are shot.
You can skimp along for a while with an engine heater. A warm engine turns over faster while cranking and lets the diesel fire off quicker.
Do you have lots of smoke after starting? If it drops off after the engine warms that means that the rings are going bad but not shot. Continuing smoke is another indication of shot rings.
David
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Your OP needs expansion. Started right up to me is 1-2 revolutions.
Hard to start to me means it is still turning after 3 revoltions without starting.
Is this what you mean as well. With nothing changed since it started right up, then post 2, a fuel lift pump or the injection pump failing makes sense.
Lepke
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Before starting put a hairdryer in the intake and while cranking. If it starts right up low compression meaning worn rings and sleeves. It doesn't mean you have to overhaul right away. Using a block heater before starting will solve the hard starts. The engine may have glow plugs. If there's no separate switch then they are usually activated while cranking the engine. Glow plug could be bad. That could explain a sudden change.
I doubt it's fuel or air in the fuel. I have seen a bad valve in the lift pump allowed fuel to flow back to the tank when the engine stopped. So extra cranking was necessary to get fuel back. Depends on the tank being lower than the engine. It's rarely a dirty fuel filter. That's the first thing many people change and all they're doing is introducing air into the system. Sometimes the top gasket of a Racor style housing will leak air. If you don't have to bleed the system, you probably don't have air in the system.
Cranking speed has an effect if it's too slow.
A diesel starts when the air temperature in the cylinders exceed the ignition temperature of diesel. That's why heating the intake or the block aids in starting.
I doubt it's fuel or air in the fuel. I have seen a bad valve in the lift pump allowed fuel to flow back to the tank when the engine stopped. So extra cranking was necessary to get fuel back. Depends on the tank being lower than the engine. It's rarely a dirty fuel filter. That's the first thing many people change and all they're doing is introducing air into the system. Sometimes the top gasket of a Racor style housing will leak air. If you don't have to bleed the system, you probably don't have air in the system.
Cranking speed has an effect if it's too slow.
A diesel starts when the air temperature in the cylinders exceed the ignition temperature of diesel. That's why heating the intake or the block aids in starting.
Mac2
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Mac2
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Another thought: My Norpro generator does not have a preheat switch. To preheat, you turn the start switch to the left for several seconds to preheat the glow plugs. Took me awhile to realize this as the generator always started right up without the glow plugs.
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Easiest, I think I would first check batteries. How old are they? Et cetera...
-Chris
-Chris
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Its usually fairly obvious if the cranking is slow by the sound. A good check if it is a battery issue is to "parallel" the house and starter batteries and see how much difference this makes.
I personally had a slow cranking problem last season and found (after other checks) that it was the starter itself. Had it repaired at a starter shop and the difference was fantastic.
captbuddy
Veteran Member
Will check the new shutdown switch the next couple of days. Just thought about just putting on before this started. I had forgot I had done that
captbuddy
Veteran Member
Guys I purchased a new glow plug thermostart and before I installed it I decided to try and start the engine since it was 75 degrees out. It cranked right up. Waited a couple days and tried it again. Weather still in low 70’s. It cranked right up. I think I just purchased a spare part. Could it have just been to cold out. We had some 20’s at night.
captbuddy
Veteran Member
Was going to install the new Thermostart but trying to make I’m removing the right one. Is this it just behind my coolant tank
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There are a few things to check:
--battery voltage AT the battery.
--Battery voltage AT the starter.
If the starter cannot get the proper voltage it cannot crank the engine quickly with slow /hard starting the result.
Use a decent voltmeter for both tests. Tests need to be performed at both the BATTERIES AND the STARTER . The meter, if you need to purchase one, does not need to be expensive but decent. If need be long leads may need to be made so YOU can see the readings easily. No need to be neat but the leads need to be long enough that you can see them while cranking ideally up in the pilot station.
If the connections between the battery(s) are not tight AND clean of oxidation and or corrosion that must be cleaned off and treatments such as NoAlox, Penetrox OR dielectric grease applied to all parts of the connections. I use pipe cleaners to apply and/or a wee brush used for cleaning. For corrosion removal you may need some abrasive tape or fine sandpaper.
Cold can and will slow the cranking if the wiring needs help. It may do fine in summer and early fall but have trouble as the weather turns colder.
Cold will also affect the batteries directly by reducing their ability to feed current and maintain voltage.
But test and clean those most important connections between the batteries AND the starter.
--battery voltage AT the battery.
--Battery voltage AT the starter.
If the starter cannot get the proper voltage it cannot crank the engine quickly with slow /hard starting the result.
Use a decent voltmeter for both tests. Tests need to be performed at both the BATTERIES AND the STARTER . The meter, if you need to purchase one, does not need to be expensive but decent. If need be long leads may need to be made so YOU can see the readings easily. No need to be neat but the leads need to be long enough that you can see them while cranking ideally up in the pilot station.
If the connections between the battery(s) are not tight AND clean of oxidation and or corrosion that must be cleaned off and treatments such as NoAlox, Penetrox OR dielectric grease applied to all parts of the connections. I use pipe cleaners to apply and/or a wee brush used for cleaning. For corrosion removal you may need some abrasive tape or fine sandpaper.
Cold can and will slow the cranking if the wiring needs help. It may do fine in summer and early fall but have trouble as the weather turns colder.
Cold will also affect the batteries directly by reducing their ability to feed current and maintain voltage.
But test and clean those most important connections between the batteries AND the starter.
