My 77 300d is hard to start and requires a couple pumps of the accelerator in order to start. Would you recommend replacing spark plugs or the pre-glow time relay??

Thanks for anything.

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1977 300D
1986 BMW 528e

Check GLOW PLUGS with an ohm meter, should read low. You have the loop style. Check fuse in relay, I think located under dash.

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83 SD

84 CD

You could also have air leaking into the fuel system, usually through IP lift pump.
I can guarantee it isn't the spark plugs, though.....

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Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

While you are at it, be sure to replace the rotor and distributor cap.

he'll need a new coil to to go with the spark plugs. you want lots of juice to run em.

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-Trevor

OBK #12
1980 300SD 333,XXX miles - Totaled
1986 Mazda RX-7 212,XXX miles - impounded and auctioned off
2005 Jeep Liberty CRD Limited 33,000- SEGR, Provent, Fumoto

You evil ones, give the guy a brake...

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Mercedes fanatic

1985 200D (w124) and totaled 190D

Sorry, the first two responses pretty well covered what's most likely wrong. A bad glowplug and/or air leaking into the fuel lines.

sorry bout that, glow plugs. i was def. not thinking

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1977 300D
1986 BMW 528e

Keep us posted.

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83 SD

84 CD

Please be aware that pumping the accelerator pedal does absolutely nothing on a Diesel.....

SB

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Diesels:
'85 300D, "Max, Blue Benz", 155K, 27.0 MPG
'84 190D 2.2, "Eva, Brown Benz", 142K, 40.2 MPG
'77 240D (parts car)
'67 Eicher ES 202 Tractor "Otto" (2cyl, Air Cooled, 30HP)
Gassers:
'94 Ford F-150, "Henry", 170K (300 Six) 17.5 MPG
'85 190E 2.3, 148K....Parts Car
'58 Dodge W300M Powerwagon (Flat Fenders) Less than 10 MPG

Right, it will only help if you hold it down while you crank the starter.

Correct, that would only flood the carburetor.

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

If all is working as designed....holding the pedal to the metal while starting does not do much for you either.....the governor inside of the FIP will be at "full rack" when the engine is stopped....and only moves off of "full rack" when the engine speed comes up to the speed set by the accelerator pedal....

there is a set of flyweights and a spring that actually control the fuel rack.....thru a system of levers "suitable linkage"

SB

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Diesels:
'85 300D, "Max, Blue Benz", 155K, 27.0 MPG
'84 190D 2.2, "Eva, Brown Benz", 142K, 40.2 MPG
'77 240D (parts car)
'67 Eicher ES 202 Tractor "Otto" (2cyl, Air Cooled, 30HP)
Gassers:
'94 Ford F-150, "Henry", 170K (300 Six) 17.5 MPG
'85 190E 2.3, 148K....Parts Car
'58 Dodge W300M Powerwagon (Flat Fenders) Less than 10 MPG

Incorrect, I suggest you read the owners manual and the Bosch highlights manual.

Will check the owners manual.....

My manual says: Depress accelerator halfway and turn idle speed adjuster counterclockwise to the stop. Then release accelerator (only on 240D) It has a scenario for Ambient temp exceeding 0*C / +32*F with no mention of the Accelerator....and a scenario for Ambient Temperature below 0*C / 32*F where it tells you to depress the accelerator.......and release accelerator slowly.....

I would think that it is MB's intent to add a little extra fuel for cold starting....because as I said as the engine speed increases the fuel rack closes to it's setpoint....which would be idle with no pressure on pedal....

don't know about a "Bosch Highlights Manual" ...but what I do know is.....after the engine stop device pulls the rack....it is in fact attached to the rack itself....but allows for rack movement....to full stop.....and the engine stops......the fuel rack will return to full fuel for starting.....the accelerator is attached to a lever on the backside of the FIP....that lever is connected inside to a set of "suitable linkage", involving a couple of pivot points and levers.....a yoke sits in a collar that is moved by the the flyweights acting against the speeder spring....this yoke moves a part of the linkage......and will move the fuel rack to Full when the set speed (by accelerator pedal) is greater than engine speed.....at rest the rack should be at Full rack until the engine gets close to the set speed of the pedal...with no movement of the pedal this will be "Idle Speed"......actual difference in speed where the fuel rack begins to close is determined by a fulcrum point and another spring and some lever action.....

Please remember that it has been nearly 10 years since I did this for a living....so I may be off a bit on this description.....but I will stand by "Full Rack at Start regardless of accelerator position.....

SB

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Diesels:
'85 300D, "Max, Blue Benz", 155K, 27.0 MPG
'84 190D 2.2, "Eva, Brown Benz", 142K, 40.2 MPG
'77 240D (parts car)
'67 Eicher ES 202 Tractor "Otto" (2cyl, Air Cooled, 30HP)
Gassers:
'94 Ford F-150, "Henry", 170K (300 Six) 17.5 MPG
'85 190E 2.3, 148K....Parts Car
'58 Dodge W300M Powerwagon (Flat Fenders) Less than 10 MPG