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Discussion Starter · #1 ·
Hey all,

Been ghosting the forums for a bit, and decided I would see if I can get some answers on an issue I am having. Thanks to the information on here, I have gotten my idle problem take care of, and a few other things, but my problem persists.

Here is the issue:

I got in the car after it sitting for a couple months. It started up fine, after all that time, but when I started to drive I noticed a loss of engine power on acceleration. It just seems to be bogged down. I ran some injector cleaner through it, but had no results. I figured I would take it for another spin today, and it had full power again right after putting in some sea foam fuel additive. I let it sit for a few hours. The wife wanted ice cream, so I figured I would take the car. Again, same issue. However, when I pump the pedal it gets up to high RPMs no problem, like there is no problem. But with the pedal to the floor consistently its bogged.

I am thinking fuel injectors. I also cannot remember when I changed the oil last. I do not let it go past 2000 miles before I change the oil.

Anyone have any thoughts or suggestions.



Much appreciated!
 

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So many possible causes! Sounds a bit like a fuel delivery problem.

Start with the no cost items such as checking your fuel pressure and definitely make sure that your throttle position switch is set up as per the service manual. Make sure that your fuel filter is not clogged, or, since it is a bit of a hassle to get to it to check it, just plan for its replacement anyway unless you have replaced it recently.

You don't provide a location. If you live in a part of the world that gets really cold weather and the car was stored during that period without the gas tank being topped up and you are using an ethanol blended fuel, you could have a gooey mess in the bottom of your gas tank due to phase separation of the accumulated moisture during the cold weather. That would require draining the tank since it is not going to go away. If you are in to doing that, then you should plan for replacement of the filter sock on the end of the fuel pick-up tube.

Beyond the preceding, everything starts to get more complicated and expensive!
 

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Discussion Starter · #5 ·
Ok, so here is an update...

Tasks performed:

- Top engine cleaned with Sea Foam Spray
- Fuel Injectors pulled and cleaned
- Sparked plugs pulled and replaced
- Oil / filter changed
- TPS maintained via post from Rainflye

After doing all that this weekend, it seems to have cleared up the issue. I think I am just going to pull the motor and do a head to toe of the entire thing this winter. I am in eastern PA, so she sits anyway. Now that the 79 rabbit motor is not sitting on the engine stand, I have some free space. I plan on a full engine overhaul. I might as well paint the thing while the engine is out as well.

Thanks to all for the advice.
 

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Discussion Starter · #6 ·
The problem returns. This time I know what is causing it! As I was driving home, I decided to flip on the fan just to get some fresh air into the car. The fan kicks on, and boom, there is the problem staring me in the face. Bogging down, and weak engine power output. It hits me. I must have low voltage on my battery! So, I am going to grab a new battery, and go through all the grounds on the electrical system. I am also going to put a new ground on the engine, since when I took a peak at the old one it looked a bit beat up.

Moral of the story. Check your battery first. I should have known this. I was once working on a 99.5 MkIV and it threw 11 short to ground codes. We did the cam position sensor, fuel pump relay, relay panel, etc, etc, before we figured out that the root cause was a bad cell on the battery. I am having a big sign made for my garage that say, "Check your damn battery!".
 

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When the engine is running, voltage is determined by the operation of the alternator and its voltage regulator, not the battery. If you can get the car started, the battery is probably not your problem. At least check your running voltage on the B+ terminal of the alternator before running off and buying a new battery. It should be in the 13.5 - 14.5 volt range. If it isn't, then you have an alternator / regulator problem.

If turning your fan on was enough to cause the voltage to drop and initiate problems on the Djet, it is likely that you have a problem with the +12v supply to the Djet. Get the wiring diagram from the service manual and connect a voltmeter to the 12v supply point on the Djet. The best location would be back probing the terminal strip on the control box itself. The next best location would be the supply off of the main FI relay in the engine compartment. Then do your test with switching the fan on and see if that causes the voltage to the Djet to drop. If it does, then check your grounds and the 12 v supply to the Djet. If it doesn't, then your problem is some place else.

I am still thinking that it might be a fuel problem.
 

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Discussion Starter · #8 ·
When the engine is running, voltage is determined by the operation of the alternator and its voltage regulator, not the battery. If you can get the car started, the battery is probably not your problem. At least check your running voltage on the B+ terminal of the alternator before running off and buying a new battery. It should be in the 13.5 - 14.5 volt range. If it isn't, then you have an alternator / regulator problem.

If turning your fan on was enough to cause the voltage to drop and initiate problems on the Djet, it is likely that you have a problem with the +12v supply to the Djet. Get the wiring diagram from the service manual and connect a voltmeter to the 12v supply point on the Djet. The best location would be back probing the terminal strip on the control box itself. The next best location would be the supply off of the main FI relay in the engine compartment. Then do your test with switching the fan on and see if that causes the voltage to the Djet to drop. If it does, then check your grounds and the 12 v supply to the Djet. If it doesn't, then your problem is some place else.

I am still thinking that it might be a fuel problem.
Thanks for the info. I will update with what I find, in case anyone else ever encounters this problem.
 

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If you think you have the same issue, grab a voltmeter and measure the voltage at the battery terminals. With the engine running, switch on your heater fan and headlights and radio and whatever other electrical loads you can turn on. Check the voltage and if it is in the 13.5 - 14.5 volt range you likely don't have a voltage related problem. However, also check the voltage on the load side of the relay which powers up the D jet controller and the fuel pump relay. If you have relay problems or wiring problems which are resulting in low voltage to the fuel pump or the D jet controller this will cause operational problems for the D jet.

Really low voltage to the fuel pump may result in the pump not being able to achieve operating pressure which results in lean operation. In addition, fuel injectors are susceptible to low voltage. They take longer to open at lower voltages which results in reduced pulse widths which cause lean running. More modern digital fuel injection systems have a curve of opening time versus operating voltage and are able to correct for this problem. I don't recall the D jet having that capability in its analog timing circuits. Deteriorated wiring and connections is the Achilles heal of the D jet system.
 

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Dalsim;

I'm with 142G on this, DJet ECU needs 12V to operate...but when checking voltage, you might want to compare V measured at Batt, to V measured at Power input to DJet controller (so terminal 87 of FI power relay, supplying power to ECU 16 and 24. Ref FI Wiring Diagram here: https://www.sw-em.com/bosch_d-jetronic_injection.htm#71_1800E_Fuel_Injection_Wiring_Diagram )...if there is more than a 0.5V difference, I'd start cleaning terminals, contacts, chassis connection (especially for DJet ECU), Batt Cables, Chassis Strap, and any other connection if only mildly involved with FI sys, to shiny metal, and reconnect these with ACZP to keep it from developing VDrops. Ref https://www.sw-em.com/anti_corrosive_paste.htm

With FI issues, I always go back to Rail pressure...it MUST be constant at 28PSI...Don't start hunting around before confirming this, else you'll be chasing your tail in frustration!!! I temporarily plumb an Oil Pressure Gauge onto the Cold Start Injector line to monitor. It's not super accurate, but will show if pressure is dropping for any reason...and that confirms a fuel delivery issue...and fuel delivery must be right (meaning constant pressure!) under ALL conditions!

BEWARE: FI Fuel Sys holds pressure even after Shut-off! Be ready for squirting fuel, and observe Fire Safety Procedures when opening pressure Rail!


Good Hunting!
 

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Dalsim;

I'm with 142G on this, DJet ECU needs 12V to operate...but when checking voltage, you might want to compare V measured at Batt, to V measured at Power input to DJet controller (so terminal 87 of FI power relay, supplying power to ECU 16 and 24. Ref FI Wiring Diagram here: https://www.sw-em.com/bosch_d-jetronic_injection.htm#71_1800E_Fuel_Injection_Wiring_Diagram )...if there is more than a 0.5V difference, I'd start cleaning terminals, contacts, chassis connection (especially for DJet ECU), Batt Cables, Chassis Strap, and any other connection if only mildly involved with FI sys, to shiny metal, and reconnect these with ACZP to keep it from developing VDrops. Ref https://www.sw-em.com/anti_corrosive_paste.htm

With FI issues, I always go back to Rail pressure...it MUST be constant at 28PSI...Don't start hunting around before confirming this, else you'll be chasing your tail in frustration!!! I temporarily plumb an Oil Pressure Gauge onto the Cold Start Injector line to monitor. It's not super accurate, but will show if pressure is dropping for any reason...and that confirms a fuel delivery issue...and fuel delivery must be right (meaning constant pressure!) under ALL conditions!

BEWARE: FI Fuel Sys holds pressure even after Shut-off! Be ready for squirting fuel, and observe Fire Safety Procedures when opening pressure Rail!


Good Hunting!
Thank you all. This is extremely helpful. I had a spare fuel filter around here and changed it as a first measure to make sure it wasn't clogged. The intake side of the filter was somewhat loose and leaking fuel so it difinitely didn't help.

Not sure if it would or wouldn't be an issue, but the car had the 1972-73 bigger filter with very large tubing and endings (12mm at least). The filter I got from CVI as replacement for the 1970-71 had 8mm big intake/exit ports, which seems to match the original square plastic one. Replaced it and went for a drive. Car felt a lot more responsive and stopped bogging after a few hundred meters.

I'll see if it is fully solved after that or if the issue comes back. In which case I'll track down electrical issues.

I alsoi intended to replace the seals on all injectors as well as I don't think they ever were serviced in the last 50 years. Are the individual injectors just "pushed in" or screwed in in some way or is the fuel rail itself what holds them in place?
 

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The individual injectors are pushed in and held in place with the retaining rings. I used some dielectric grease on the seals to ease installation. If you don’t have them it may be an opportunity to add the phenolic washers which require a larger o-ring under the injector holders. The phenolic washer retrofit is intended to relieve hot start issues.

The original 28 PSI spec for fuel pressure was changed to 30 PSI in a subsequent service bulletin by Volvo.
 

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Dalsi;

Is that Filter located before of after the FuPu? ..if Before it could have been sucking air, which if excessive would lead to (partial or intermittent) fuel starvation...if After it would be subjected to high pressure so would surely have leaked and probably been detectable by fuel stink (and wet patches).

There is nothing sacred about FuFi size, but obviously a smaller filter would get blocked sooner if a lot of debris was coming along, and the plumbing must fit...when I had my rust-in tank issues, I got pretty good at rapid FuFi changing...and I had to change them so often that I'd even reuse them after rinsing the rust particles out (and capturing on a white paper towel to inspect)...once no more particles came out, I put in a clean new FuFi and had peace, AND constant fuel pressure and reliable operation finally!

Good Hunting!
 

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Dalsi;

Is that Filter located before of after the FuPu? ..if Before it could have been sucking air, which if excessive would lead to (partial or intermittent) fuel starvation...if After it would be subjected to high pressure so would surely have leaked and probably been detectable by fuel stink (and wet patches).

There is nothing sacred about FuFi size, but obviously a smaller filter would get blocked sooner if a lot of debris was coming along, and the plumbing must fit...when I had my rust-in tank issues, I got pretty good at rapid FuFi changing...and I had to change them so often that I'd even reuse them after rinsing the rust particles out (and capturing on a white paper towel to inspect)...once no more particles came out, I put in a clean new FuFi and had peace, AND constant fuel pressure and reliable operation finally!

Good Hunting!
Fuel filter is before the fuel pump. It was installed by a previous tech with giant worm screw clamps that has damaged the rubber lines, in addition to the hoses being to big for the Fuel Filter fittings... Either the fuel filter was too clogged (not likely from rust however as my fuel tank was replaced like 5-6 years ago with a reproduction one (either from Scandcar or IPD I cannot remember)). As you mention, could be from sucking air under higher pressure. There definitely was lingering fresh gasoline smell in the garage when I had it in the garage during the winter.
 

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The individual injectors are pushed in and held in place with the retaining rings. I used some dielectric grease on the seals to ease installation. If you don't have them it may be an opportunity to add the phenolic washers which require a larger o-ring under the injector holders. The phenolic washer retrofit is intended to relieve hot start issues.

The original 28 PSI spec for fuel pressure was changed to 30 PSI in a subsequent service bulletin by Volvo.
Are the phenolic washers the PN# 957173? (From CVI catalog)
I have already ordered a set of 4 of those along with 4 of each of the other seals #419785 (lower seals - small) and #419784 (upper seals - large).

When pulling the injectors, if you can just pull them out to switch the washer and seals, do I even need to purge the gas line or can I do a "hotswap" of the seals/washers?
 

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957173 are not the phenolic washers. For some bizarre reason CVI does not catalog them. The part number is 962658

http://212.247.61.152/us/main.aspx?page=articlelist&requery=1&searchstr=962658&searchfld=

You need 8 of them. One below the injector holder and one above the injector holder (under the bolt and washer) so that the injector holder is sandwiched between the phenolic washers. The correct fat rubber O ring between the head and the injector holder for use with the phenolic washers is 960168.

http://212.247.61.152/us/main.aspx?page=article&artno=960168

VP's price for the phenolic washers is a bit high. Search a bit and you can find them for less. There used to be a retrofit kit which included the 8 phenolic washers and the 4 O rings for a nice price; but, I don't have the number. IPD might still list it.

Once the large locking collars around the injector bodies are released, you should be able to pull the injectors up and out of the holders without having to pull the injectors off of the rail. You may need to unbolt the cold start injector from the manifold so that the hose tap to the cold start valve has enough slack to allow you to pull the rail back. You may also need to remove the clips retaining the fuel hoses to the firewall to allow for more movement.

If the injectors have not been removed in the last 5 years, they will likely bond to the rubber pintel seals in the injector holder making removal a bit of a struggle. Don't yank on just one injector, try to pull each one up a bit so that they are all coming out evenly. If you yank on one injector and it pops loose with the others stuck in place you risk bending / kinking the fuel rail and then you are truly f****d. Once the injectors are released from the holders you are then free to unbolt the holder from the head and install the washers and new O ring.

You have the new pintel seals and the big rubber retainer ring on order. As noted by craig300, grease the rings and seals up with lots of silicone grease (dielectric tune up grease is perfect) to make things go back together easier (not necessarily easily).

If the injectors are original, while they are out and easier to inspect have a look at the rubber stub hoses that connect the injector to the rail. These stubs can deteriorate and start to leak, especially where the hose fits under the compression fitting on the injector. The injector does have a barbed fitting under the compression fitting so you can replace the stubs and use banded clamps to hold the stub hose on each end. You will carefully have to use a hack saw or dremel style cut-off wheel to cut off the old compression fitting. Unfortunately I cannot advise on good replacement fuel line. I am currently struggling to find 5/16" fuel line that lasts more than 3-4 years before it gets hard and starts to crack.
 
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